docs(features): add completion note for Phase 2

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

GermanApp/Application/DTOs/LessonDto.cs

@@ -10,8 +10,11 @@ public record LessonDto(
     int Id,
     string Title,
     string Description,
-    int Level,
+    int LevelId,
-    string LevelDescription,
+    string LevelName,
+    string LevelCode,
+    int Order,
+    string Topic,
     DateTime CreatedAt,
     DateTime? UpdatedAt);
 
@@ -21,7 +24,9 @@ public record LessonDto(
 public record CreateLessonDto(
     string Title,
     string Description,
-    int Level);
+    int LevelId,
+    int Order,
+    string Topic);
 
 /// <summary>
 /// Data Transfer Object for updating an existing Lesson.
@@ -29,7 +34,9 @@ public record CreateLessonDto(
 public record UpdateLessonDto(
     string Title,
     string Description,
-    int Level);
+    int LevelId,
+    int Order,
+    string Topic);
 
 /// <summary>
 /// Extension methods for mapping between Lesson entity and DTOs.
@@ -40,21 +47,23 @@ public static class LessonDtoExtensions
         lesson.Id,
         lesson.Title,
         lesson.Description,
-        lesson.Level,
+        lesson.LevelId,
-        GetLevelDescription(lesson.Level),
+        lesson.Level?.Name ?? "Unknown",
+        lesson.Level?.Code ?? "??",
+        lesson.Order,
+        lesson.Topic,
         lesson.CreatedAt,
         lesson.UpdatedAt);
 
-    private static string GetLevelDescription(int level) => level switch
-    {
-        1 => "A1 (Beginner)",
-        2 => "A2 (Elementary)",
-        3 => "B1 (Intermediate)",
-        4 => "B2 (Upper Intermediate)",
-        5 => "C1 (Advanced)",
-        _ => "Unknown"
-    };
-
     public static Lesson ToEntity(this CreateLessonDto dto) =>
-        Lesson.Create(dto.Title, dto.Description, dto.Level);
+        Lesson.Create(dto.LevelId, dto.Title, dto.Order, dto.Topic, dto.Description);
+
+    public static void UpdateFromDto(this Lesson lesson, UpdateLessonDto dto)
+    {
+        lesson.UpdateTitle(dto.Title);
+        lesson.UpdateDescription(dto.Description);
+        lesson.UpdateLevel(dto.LevelId);
+        lesson.UpdateOrder(dto.Order);
+        lesson.UpdateTopic(dto.Topic);
+    }
 }

GermanApp/Application/DTOs/LevelDto.cs

@@ -0,0 +1,51 @@
+using GermanApp.Domain.Entities;
+
+namespace GermanApp.Application.DTOs;
+
+/// <summary>
+/// Data Transfer Object for Level - used for API responses.
+/// This is a read-only representation of a Level entity.
+/// </summary>
+public record LevelDto(
+    int Id,
+    string Name,
+    string Code,
+    int Order);
+
+/// <summary>
+/// Data Transfer Object for creating a new Level.
+/// </summary>
+public record CreateLevelDto(
+    string Name,
+    string Code,
+    int Order);
+
+/// <summary>
+/// Data Transfer Object for updating an existing Level.
+/// </summary>
+public record UpdateLevelDto(
+    string Name,
+    string Code,
+    int Order);
+
+/// <summary>
+/// Extension methods for mapping between Level entity and DTOs.
+/// </summary>
+public static class LevelDtoExtensions
+{
+    public static LevelDto ToDto(this Level level) => new(
+        level.Id,
+        level.Name,
+        level.Code,
+        level.Order);
+
+    public static Level ToEntity(this CreateLevelDto dto) =>
+        Level.Create(dto.Name, dto.Code, dto.Order);
+
+    public static void UpdateFromDto(this Level level, UpdateLevelDto dto)
+    {
+        level.UpdateName(dto.Name);
+        level.UpdateCode(dto.Code);
+        level.UpdateOrder(dto.Order);
+    }
+}

GermanApp/Application/DTOs/UserProgressDto.cs

@@ -0,0 +1,80 @@
+using GermanApp.Domain.Entities;
+
+namespace GermanApp.Application.DTOs;
+
+/// <summary>
+/// Data Transfer Object for UserProgress - used for API responses.
+/// This is a read-only representation of a UserProgress entity.
+/// </summary>
+public record UserProgressDto(
+    int Id,
+    int UserId,
+    int LessonId,
+    bool IsCompleted,
+    int QuizScore,
+    DateTime LastAttemptDate,
+    string? LessonTitle = null,
+    string? LevelName = null,
+    string? LevelCode = null);
+
+/// <summary>
+/// Data Transfer Object for creating/updating user progress.
+/// </summary>
+public record UpdateUserProgressDto(
+    int LessonId,
+    bool IsCompleted,
+    int QuizScore);
+
+/// <summary>
+/// Data Transfer Object for level completion summary.
+/// </summary>
+public record LevelCompletionDto(
+    int LevelId,
+    string LevelName,
+    string LevelCode,
+    int TotalLessons,
+    int CompletedLessons,
+    double CompletionPercentage);
+
+/// <summary>
+/// Extension methods for mapping between UserProgress entity and DTOs.
+/// </summary>
+public static class UserProgressDtoExtensions
+{
+    public static UserProgressDto ToDto(this UserProgress userProgress) => new(
+        userProgress.Id,
+        userProgress.UserId,
+        userProgress.LessonId,
+        userProgress.IsCompleted,
+        userProgress.QuizScore,
+        userProgress.LastAttemptDate,
+        userProgress.Lesson?.Title,
+        userProgress.Lesson?.Level?.Name,
+        userProgress.Lesson?.Level?.Code);
+
+    public static UserProgress ToEntity(this UpdateUserProgressDto dto, int userId)
+    {
+        var progress = UserProgress.Create(userId, dto.LessonId);
+        if (dto.IsCompleted)
+        {
+            progress.MarkAsCompleted(dto.QuizScore);
+        }
+        else
+        {
+            progress.UpdateQuizScore(dto.QuizScore);
+        }
+        return progress;
+    }
+
+    public static void UpdateFromDto(this UserProgress userProgress, UpdateUserProgressDto dto)
+    {
+        if (dto.IsCompleted)
+        {
+            userProgress.MarkAsCompleted(dto.QuizScore);
+        }
+        else
+        {
+            userProgress.UpdateQuizScore(dto.QuizScore);
+        }
+    }
+}

GermanApp/Application/Services/LessonService.cs

@@ -0,0 +1,159 @@
+using GermanApp.Application.DTOs;
+using GermanApp.Domain.Entities;
+using GermanApp.Domain.Interfaces;
+
+namespace GermanApp.Application.Services;
+
+/// <summary>
+/// Application service for managing lessons.
+/// This is part of the Application layer.
+/// </summary>
+public class LessonService
+{
+    private readonly ILessonRepository _lessonRepository;
+    private readonly ILevelRepository _levelRepository;
+
+    public LessonService(ILessonRepository lessonRepository, ILevelRepository levelRepository)
+    {
+        _lessonRepository = lessonRepository;
+        _levelRepository = levelRepository;
+    }
+
+    /// <summary>
+    /// Gets all lessons.
+    /// </summary>
+    public async Task<IReadOnlyList<LessonDto>> GetAllLessonsAsync(CancellationToken cancellationToken = default)
+    {
+        var lessons = await _lessonRepository.GetAllAsync(cancellationToken);
+        return lessons.Select(l => l.ToDto()).ToList();
+    }
+
+    /// <summary>
+    /// Gets all lessons ordered by level and lesson order.
+    /// </summary>
+    public async Task<IReadOnlyList<LessonDto>> GetAllOrderedLessonsAsync(CancellationToken cancellationToken = default)
+    {
+        var lessons = await _lessonRepository.GetAllOrderedAsync(cancellationToken);
+        return lessons.Select(l => l.ToDto()).ToList();
+    }
+
+    /// <summary>
+    /// Gets a lesson by its ID.
+    /// </summary>
+    public async Task<LessonDto?> GetLessonByIdAsync(int id, CancellationToken cancellationToken = default)
+    {
+        var lesson = await _lessonRepository.GetByIdAsync(id, cancellationToken);
+        return lesson?.ToDto();
+    }
+
+    /// <summary>
+    /// Gets lessons by level ID.
+    /// </summary>
+    public async Task<IReadOnlyList<LessonDto>> GetLessonsByLevelAsync(int levelId, CancellationToken cancellationToken = default)
+    {
+        var lessons = await _lessonRepository.GetByLevelAsync(levelId, cancellationToken);
+        return lessons.Select(l => l.ToDto()).ToList();
+    }
+
+    /// <summary>
+    /// Gets beginner lessons (A1 and A2 - levels 1 and 2).
+    /// </summary>
+    public async Task<IReadOnlyList<LessonDto>> GetBeginnerLessonsAsync(CancellationToken cancellationToken = default)
+    {
+        var level1Lessons = await _lessonRepository.GetByLevelAsync(1, cancellationToken);
+        var level2Lessons = await _lessonRepository.GetByLevelAsync(2, cancellationToken);
+        var allLessons = level1Lessons.Concat(level2Lessons)
+            .OrderBy(l => l.LevelId)
+            .ThenBy(l => l.Order)
+            .ToList();
+        return allLessons.Select(l => l.ToDto()).ToList();
+    }
+
+    /// <summary>
+    /// Gets advanced lessons (B2 and C1 - levels 4 and 5).
+    /// </summary>
+    public async Task<IReadOnlyList<LessonDto>> GetAdvancedLessonsAsync(CancellationToken cancellationToken = default)
+    {
+        var level4Lessons = await _lessonRepository.GetByLevelAsync(4, cancellationToken);
+        var level5Lessons = await _lessonRepository.GetByLevelAsync(5, cancellationToken);
+        var allLessons = level4Lessons.Concat(level5Lessons)
+            .OrderBy(l => l.LevelId)
+            .ThenBy(l => l.Order)
+            .ToList();
+        return allLessons.Select(l => l.ToDto()).ToList();
+    }
+
+    /// <summary>
+    /// Creates a new lesson.
+    /// </summary>
+    public async Task<LessonDto> CreateLessonAsync(CreateLessonDto dto, CancellationToken cancellationToken = default)
+    {
+        // Validate that the level exists
+        var level = await _levelRepository.GetByIdAsync(dto.LevelId, cancellationToken);
+        if (level == null)
+            throw new ArgumentException("Level does not exist");
+
+        var lesson = dto.ToEntity();
+        var createdLesson = await _lessonRepository.AddAsync(lesson, cancellationToken);
+        return createdLesson.ToDto();
+    }
+
+    /// <summary>
+    /// Updates an existing lesson.
+    /// </summary>
+    public async Task<LessonDto?> UpdateLessonAsync(int id, UpdateLessonDto dto, CancellationToken cancellationToken = default)
+    {
+        var lesson = await _lessonRepository.GetByIdAsync(id, cancellationToken);
+        if (lesson == null)
+            return null;
+
+        // Validate that the level exists
+        var level = await _levelRepository.GetByIdAsync(dto.LevelId, cancellationToken);
+        if (level == null)
+            throw new ArgumentException("Level does not exist");
+
+        lesson.UpdateFromDto(dto);
+        await _lessonRepository.UpdateAsync(lesson, cancellationToken);
+        return lesson.ToDto();
+    }
+
+    /// <summary>
+    /// Deletes a lesson by its ID.
+    /// </summary>
+    public async Task<bool> DeleteLessonAsync(int id, CancellationToken cancellationToken = default)
+    {
+        var lesson = await _lessonRepository.GetByIdAsync(id, cancellationToken);
+        if (lesson == null)
+            return false;
+
+        await _lessonRepository.DeleteAsync(lesson, cancellationToken);
+        return true;
+    }
+
+    /// <summary>
+    /// Gets the first lesson in a level.
+    /// </summary>
+    public async Task<LessonDto?> GetFirstLessonInLevelAsync(int levelId, CancellationToken cancellationToken = default)
+    {
+        var lesson = await _lessonRepository.GetFirstLessonInLevelAsync(levelId, cancellationToken);
+        return lesson?.ToDto();
+    }
+
+    /// <summary>
+    /// Gets the next lesson after the specified one.
+    /// </summary>
+    public async Task<LessonDto?> GetNextLessonAsync(int currentLessonId, CancellationToken cancellationToken = default)
+    {
+        var lesson = await _lessonRepository.GetNextLessonAsync(currentLessonId, cancellationToken);
+        return lesson?.ToDto();
+    }
+
+    /// <summary>
+    /// Gets lessons that the user can access (based on completion of previous lessons).
+    /// </summary>
+    public async Task<IReadOnlyList<LessonDto>> GetAccessibleLessonsAsync(int userId, CancellationToken cancellationToken = default)
+    {
+        var lessons = await _lessonRepository.GetAccessibleLessonsAsync(userId, cancellationToken);
+        return lessons.Select(l => l.ToDto()).ToList();
+    }
+}

GermanApp/Application/Services/LevelService.cs

@@ -0,0 +1,101 @@
+using GermanApp.Application.DTOs;
+using GermanApp.Domain.Entities;
+using GermanApp.Domain.Interfaces;
+
+namespace GermanApp.Application.Services;
+
+/// <summary>
+/// Application service for managing CEFR levels.
+/// This is part of the Application layer.
+/// </summary>
+public class LevelService
+{
+    private readonly ILevelRepository _levelRepository;
+
+    public LevelService(ILevelRepository levelRepository)
+    {
+        _levelRepository = levelRepository;
+    }
+
+    /// <summary>
+    /// Gets all CEFR levels ordered by their sort order.
+    /// </summary>
+    public async Task<IReadOnlyList<LevelDto>> GetAllLevelsAsync(CancellationToken cancellationToken = default)
+    {
+        var levels = await _levelRepository.GetAllOrderedAsync(cancellationToken);
+        return levels.Select(l => l.ToDto()).ToList();
+    }
+
+    /// <summary>
+    /// Gets a level by its ID.
+    /// </summary>
+    public async Task<LevelDto?> GetLevelByIdAsync(int id, CancellationToken cancellationToken = default)
+    {
+        var level = await _levelRepository.GetByIdAsync(id, cancellationToken);
+        return level?.ToDto();
+    }
+
+    /// <summary>
+    /// Gets a level by its code (e.g., "A1", "B2").
+    /// </summary>
+    public async Task<LevelDto?> GetLevelByCodeAsync(string code, CancellationToken cancellationToken = default)
+    {
+        var level = await _levelRepository.GetByCodeAsync(code, cancellationToken);
+        return level?.ToDto();
+    }
+
+    /// <summary>
+    /// Creates a new CEFR level.
+    /// </summary>
+    public async Task<LevelDto> CreateLevelAsync(CreateLevelDto dto, CancellationToken cancellationToken = default)
+    {
+        var level = dto.ToEntity();
+        var createdLevel = await _levelRepository.AddAsync(level, cancellationToken);
+        return createdLevel.ToDto();
+    }
+
+    /// <summary>
+    /// Updates an existing CEFR level.
+    /// </summary>
+    public async Task<LevelDto?> UpdateLevelAsync(int id, UpdateLevelDto dto, CancellationToken cancellationToken = default)
+    {
+        var level = await _levelRepository.GetByIdAsync(id, cancellationToken);
+        if (level == null)
+            return null;
+
+        level.UpdateFromDto(dto);
+        await _levelRepository.UpdateAsync(level, cancellationToken);
+        return level.ToDto();
+    }
+
+    /// <summary>
+    /// Deletes a CEFR level by its ID.
+    /// </summary>
+    public async Task<bool> DeleteLevelAsync(int id, CancellationToken cancellationToken = default)
+    {
+        var level = await _levelRepository.GetByIdAsync(id, cancellationToken);
+        if (level == null)
+            return false;
+
+        await _levelRepository.DeleteAsync(level, cancellationToken);
+        return true;
+    }
+
+    /// <summary>
+    /// Gets the first level (lowest order number) - typically A1.
+    /// </summary>
+    public async Task<LevelDto?> GetFirstLevelAsync(CancellationToken cancellationToken = default)
+    {
+        var level = await _levelRepository.GetFirstLevelAsync(cancellationToken);
+        return level?.ToDto();
+    }
+
+    /// <summary>
+    /// Gets the next level after the specified one.
+    /// </summary>
+    public async Task<LevelDto?> GetNextLevelAsync(int currentLevelId, CancellationToken cancellationToken = default)
+    {
+        var level = await _levelRepository.GetNextLevelAsync(currentLevelId, cancellationToken);
+        return level?.ToDto();
+    }
+}

GermanApp/Application/Services/ProgressService.cs

@@ -0,0 +1,206 @@
+using GermanApp.Application.DTOs;
+using GermanApp.Domain.Entities;
+using GermanApp.Domain.Interfaces;
+
+namespace GermanApp.Application.Services;
+
+/// <summary>
+/// Application service for managing user progress through lessons.
+/// This is part of the Application layer.
+/// </summary>
+public class ProgressService
+{
+    private readonly IUserProgressRepository _userProgressRepository;
+    private readonly ILessonRepository _lessonRepository;
+    private readonly ILevelRepository _levelRepository;
+
+    public ProgressService(
+        IUserProgressRepository userProgressRepository,
+        ILessonRepository lessonRepository,
+        ILevelRepository levelRepository)
+    {
+        _userProgressRepository = userProgressRepository;
+        _lessonRepository = lessonRepository;
+        _levelRepository = levelRepository;
+    }
+
+    /// <summary>
+    /// Gets user progress for a specific lesson.
+    /// </summary>
+    public async Task<UserProgressDto?> GetUserProgressAsync(int userId, int lessonId, CancellationToken cancellationToken = default)
+    {
+        var progress = await _userProgressRepository.GetByUserAndLessonAsync(userId, lessonId, cancellationToken);
+        return progress?.ToDto();
+    }
+
+    /// <summary>
+    /// Gets all progress records for a user.
+    /// </summary>
+    public async Task<IReadOnlyList<UserProgressDto>> GetUserProgressAsync(int userId, CancellationToken cancellationToken = default)
+    {
+        var progressRecords = await _userProgressRepository.GetByUserAsync(userId, cancellationToken);
+        return progressRecords.Select(p => p.ToDto()).ToList();
+    }
+
+    /// <summary>
+    /// Gets progress for all lessons in a specific level for a user.
+    /// </summary>
+    public async Task<IReadOnlyList<UserProgressDto>> GetUserProgressByLevelAsync(int userId, int levelId, CancellationToken cancellationToken = default)
+    {
+        var progressRecords = await _userProgressRepository.GetByUserAndLevelAsync(userId, levelId, cancellationToken);
+        return progressRecords.Select(p => p.ToDto()).ToList();
+    }
+
+    /// <summary>
+    /// Checks if a user has completed a lesson.
+    /// </summary>
+    public async Task<bool> HasUserCompletedLessonAsync(int userId, int lessonId, CancellationToken cancellationToken = default)
+    {
+        return await _userProgressRepository.HasUserCompletedLessonAsync(userId, lessonId, cancellationToken);
+    }
+
+    /// <summary>
+    /// Marks a lesson as completed for a user with a quiz score.
+    /// </summary>
+    public async Task<UserProgressDto> MarkLessonAsCompletedAsync(int userId, int lessonId, int quizScore, CancellationToken cancellationToken = default)
+    {
+        var progress = await _userProgressRepository.GetByUserAndLessonAsync(userId, lessonId, cancellationToken);
+        
+        if (progress == null)
+        {
+            // Create new progress record
+            progress = UserProgress.Create(userId, lessonId);
+            progress.MarkAsCompleted(quizScore);
+            await _userProgressRepository.AddAsync(progress, cancellationToken);
+        }
+        else
+        {
+            // Update existing progress record
+            progress.MarkAsCompleted(quizScore);
+            await _userProgressRepository.UpdateAsync(progress, cancellationToken);
+        }
+        
+        return progress.ToDto();
+    }
+
+    /// <summary>
+    /// Updates user progress for a lesson without marking as completed.
+    /// </summary>
+    public async Task<UserProgressDto> UpdateUserProgressAsync(int userId, UpdateUserProgressDto dto, CancellationToken cancellationToken = default)
+    {
+        var progress = await _userProgressRepository.GetByUserAndLessonAsync(userId, dto.LessonId, cancellationToken);
+        
+        if (progress == null)
+        {
+            // Create new progress record
+            progress = dto.ToEntity(userId);
+            await _userProgressRepository.AddAsync(progress, cancellationToken);
+        }
+        else
+        {
+            // Update existing progress record
+            progress.UpdateFromDto(dto);
+            await _userProgressRepository.UpdateAsync(progress, cancellationToken);
+        }
+        
+        return progress.ToDto();
+    }
+
+    /// <summary>
+    /// Resets user progress for a lesson.
+    /// </summary>
+    public async Task<bool> ResetLessonProgressAsync(int userId, int lessonId, CancellationToken cancellationToken = default)
+    {
+        var progress = await _userProgressRepository.GetByUserAndLessonAsync(userId, lessonId, cancellationToken);
+        if (progress == null)
+            return false;
+
+        progress.Reset();
+        await _userProgressRepository.UpdateAsync(progress, cancellationToken);
+        return true;
+    }
+
+    /// <summary>
+    /// Gets the user's average score for a level.
+    /// </summary>
+    public async Task<double> GetAverageScoreForLevelAsync(int userId, int levelId, CancellationToken cancellationToken = default)
+    {
+        return await _userProgressRepository.GetAverageScoreForLevelAsync(userId, levelId, cancellationToken);
+    }
+
+    /// <summary>
+    /// Gets the percentage of lessons completed in a level.
+    /// </summary>
+    public async Task<double> GetLevelCompletionPercentageAsync(int userId, int levelId, CancellationToken cancellationToken = default)
+    {
+        return await _userProgressRepository.GetLevelCompletionPercentageAsync(userId, levelId, cancellationToken);
+    }
+
+    /// <summary>
+    /// Gets level completion summaries for a user.
+    /// </summary>
+    public async Task<IReadOnlyList<LevelCompletionDto>> GetLevelCompletionsAsync(int userId, CancellationToken cancellationToken = default)
+    {
+        var levels = await _levelRepository.GetAllOrderedAsync(cancellationToken);
+        var completions = new List<LevelCompletionDto>();
+
+        foreach (var level in levels)
+        {
+            var lessons = await _lessonRepository.GetByLevelAsync(level.Id, cancellationToken);
+            var completedCount = 0;
+            
+            foreach (var lesson in lessons)
+            {
+                var hasCompleted = await _userProgressRepository.HasUserCompletedLessonAsync(userId, lesson.Id, cancellationToken);
+                if (hasCompleted)
+                    completedCount++;
+            }
+            
+            var percentage = lessons.Count > 0 
+                ? (double)completedCount / lessons.Count * 100 
+                : 0;
+            
+            completions.Add(new LevelCompletionDto(
+                level.Id,
+                level.Name,
+                level.Code,
+                lessons.Count,
+                completedCount,
+                percentage
+            ));
+        }
+        
+        return completions;
+    }
+
+    /// <summary>
+    /// Gets lessons that the user can access (completed previous lessons or first in level).
+    /// </summary>
+    public async Task<IReadOnlyList<LessonDto>> GetAccessibleLessonsAsync(int userId, CancellationToken cancellationToken = default)
+    {
+        var lessons = await _lessonRepository.GetAccessibleLessonsAsync(userId, cancellationToken);
+        return lessons.Select(l => l.ToDto()).ToList();
+    }
+
+    /// <summary>
+    /// Checks if the next lesson in a level is unlocked for the user.
+    /// </summary>
+    public async Task<bool> IsNextLessonUnlockedAsync(int userId, int currentLessonId, CancellationToken cancellationToken = default)
+    {
+        var currentLesson = await _lessonRepository.GetByIdAsync(currentLessonId, cancellationToken);
+        if (currentLesson == null)
+            return false;
+
+        // If this is the first lesson in the level, the next one is always unlocked
+        var firstLesson = await _lessonRepository.GetFirstLessonInLevelAsync(currentLesson.LevelId, cancellationToken);
+        if (firstLesson?.Id == currentLessonId)
+        {
+            var nextLesson = await _lessonRepository.GetNextLessonAsync(currentLessonId, cancellationToken);
+            return nextLesson != null;
+        }
+
+        // Check if the user has completed the current lesson
+        var hasCompleted = await _userProgressRepository.HasUserCompletedLessonAsync(userId, currentLessonId, cancellationToken);
+        return hasCompleted;
+    }
+}

GermanApp/Application/UseCases/Commands/CreateLessonCommand.cs

@@ -29,7 +29,7 @@ public class CreateLessonCommandHandler : ICommandHandler<CreateLessonCommand, L
         var lesson = command.LessonData.ToEntity();
 
         // Validate business rules (could be extracted to a validator)
-        if (lesson.Level < 1 || lesson.Level > 5)
+        if (lesson.LevelId < 1 || lesson.LevelId > 5)
         {
             throw new ValidationException("Level must be between 1 and 5");
         }

GermanApp/Domain/Entities/Lesson.cs

@@ -1,20 +1,23 @@
 namespace GermanApp.Domain.Entities;
 
 /// <summary>
-/// Represents a German language lesson in the system.
+/// Represents a lesson in the DeutschLernen system.
+/// Lessons are organized within CEFR levels and must be completed in order.
 /// </summary>
 public class Lesson
 {
-    // Private setter for domain behavior, but internal for EF Core
     public int Id { get; private set; }
+    public int LevelId { get; private set; }
     public string Title { get; private set; } = string.Empty;
+    public int Order { get; private set; }
+    public string Topic { get; private set; } = string.Empty;
     public string Description { get; private set; } = string.Empty;
-    public int Level { get; private set; }
+    public bool IsActive { get; private set; } = true;
     public DateTime CreatedAt { get; private set; }
     public DateTime? UpdatedAt { get; private set; }
 
-    // Navigation properties would go here in EF Core
+    // Navigation property (EF Core will handle this)
-    // public ICollection<VocabularyWord> Words { get; private set; }
+    public virtual Level? Level { get; private set; }
 
     /// <summary>
     /// Constructor for EF Core deserialization.
@@ -24,35 +27,84 @@ public class Lesson
     /// <summary>
     /// Factory method to create a new lesson.
     /// </summary>
-    public static Lesson Create(string title, string description, int level)
+    /// <param name="levelId">ID of the parent level</param>
+    /// <param name="title">Title of the lesson</param>
+    /// <param name="order">Sort order within the level</param>
+    /// <param name="topic">Main topic covered in the lesson</param>
+    /// <param name="description">Description of what the lesson covers</param>
+    public static Lesson Create(int levelId, string title, int order, string topic, string description = "")
     {
         return new Lesson
         {
+            LevelId = levelId,
             Title = title,
+            Order = order,
+            Topic = topic,
             Description = description,
-            Level = level,
             CreatedAt = DateTime.UtcNow
         };
     }
 
     /// <summary>
-    /// Updates the lesson details.
+    /// Updates the lesson's title.
     /// </summary>
-    public void Update(string title, string description, int level)
+    public void UpdateTitle(string newTitle)
     {
-        Title = title;
+        Title = newTitle;
-        Description = description;
-        Level = level;
         UpdatedAt = DateTime.UtcNow;
     }
 
     /// <summary>
-    /// Domain behavior: Check if lesson is at beginner level.
+    /// Updates the lesson's topic.
     /// </summary>
-    public bool IsBeginnerLevel() => Level <= 2;
+    public void UpdateTopic(string newTopic)
+    {
+        Topic = newTopic;
+        UpdatedAt = DateTime.UtcNow;
+    }
 
     /// <summary>
-    /// Domain behavior: Check if lesson is at advanced level.
+    /// Updates the lesson's description.
     /// </summary>
-    public bool IsAdvancedLevel() => Level >= 4;
+    public void UpdateDescription(string newDescription)
+    {
+        Description = newDescription;
+        UpdatedAt = DateTime.UtcNow;
+    }
+
+    /// <summary>
+    /// Updates the lesson's sort order.
+    /// </summary>
+    public void UpdateOrder(int newOrder)
+    {
+        Order = newOrder;
+        UpdatedAt = DateTime.UtcNow;
+    }
+
+    /// <summary>
+    /// Updates the lesson's level.
+    /// </summary>
+    public void UpdateLevel(int newLevelId)
+    {
+        LevelId = newLevelId;
+        UpdatedAt = DateTime.UtcNow;
+    }
+
+    /// <summary>
+    /// Activates the lesson.
+    /// </summary>
+    public void Activate()
+    {
+        IsActive = true;
+        UpdatedAt = DateTime.UtcNow;
+    }
+
+    /// <summary>
+    /// Deactivates the lesson.
+    /// </summary>
+    public void Deactivate()
+    {
+        IsActive = false;
+        UpdatedAt = DateTime.UtcNow;
+    }
 }

GermanApp/Domain/Entities/Level.cs

@@ -0,0 +1,57 @@
+namespace GermanApp.Domain.Entities;
+
+/// <summary>
+/// Represents a CEFR level in the DeutschLernen system (A1, A2, B1, B2, C1).
+/// </summary>
+public class Level
+{
+    public int Id { get; private set; }
+    public string Name { get; private set; } = string.Empty;
+    public string Code { get; private set; } = string.Empty;
+    public int Order { get; private set; }
+
+    /// <summary>
+    /// Constructor for EF Core deserialization.
+    /// </summary>
+    private Level() { }
+
+    /// <summary>
+    /// Factory method to create a new level.
+    /// </summary>
+    /// <param name="name">Display name of the level (e.g., "Beginner A1")</param>
+    /// <param name="code">Short code for the level (e.g., "A1")</param>
+    /// <param name="order">Sort order of the level</param>
+    public static Level Create(string name, string code, int order)
+    {
+        return new Level
+        {
+            Name = name,
+            Code = code.ToUpperInvariant(),
+            Order = order
+        };
+    }
+
+    /// <summary>
+    /// Updates the level's display name.
+    /// </summary>
+    public void UpdateName(string newName)
+    {
+        Name = newName;
+    }
+
+    /// <summary>
+    /// Updates the level's code.
+    /// </summary>
+    public void UpdateCode(string newCode)
+    {
+        Code = newCode.ToUpperInvariant();
+    }
+
+    /// <summary>
+    /// Updates the level's sort order.
+    /// </summary>
+    public void UpdateOrder(int newOrder)
+    {
+        Order = newOrder;
+    }
+}

GermanApp/Domain/Entities/UserProgress.cs

@@ -0,0 +1,82 @@
+namespace GermanApp.Domain.Entities;
+
+/// <summary>
+/// Represents a user's progress through lessons.
+/// Tracks completion status and quiz scores.
+/// </summary>
+public class UserProgress
+{
+    public int Id { get; private set; }
+    public int UserId { get; private set; }
+    public int LessonId { get; private set; }
+    public bool IsCompleted { get; private set; }
+    public int QuizScore { get; private set; }
+    public DateTime LastAttemptDate { get; private set; }
+
+    // Navigation properties
+    public virtual User? User { get; private set; }
+    public virtual Lesson? Lesson { get; private set; }
+
+    /// <summary>
+    /// Constructor for EF Core deserialization.
+    /// </summary>
+    private UserProgress() { }
+
+    /// <summary>
+    /// Factory method to create a new user progress record.
+    /// </summary>
+    /// <param name="userId">ID of the user</param>
+    /// <param name="lessonId">ID of the lesson</param>
+    public static UserProgress Create(int userId, int lessonId)
+    {
+        return new UserProgress
+        {
+            UserId = userId,
+            LessonId = lessonId,
+            IsCompleted = false,
+            QuizScore = 0,
+            LastAttemptDate = DateTime.UtcNow
+        };
+    }
+
+    /// <summary>
+    /// Marks the lesson as completed.
+    /// </summary>
+    /// <param name="quizScore">The score achieved on the quiz (0-100)</param>
+    public void MarkAsCompleted(int quizScore)
+    {
+        if (quizScore < 0 || quizScore > 100)
+            throw new ArgumentOutOfRangeException(nameof(quizScore), "Score must be between 0 and 100");
+
+        IsCompleted = true;
+        QuizScore = quizScore;
+        LastAttemptDate = DateTime.UtcNow;
+    }
+
+    /// <summary>
+    /// Updates the quiz score without marking as completed.
+    /// </summary>
+    public void UpdateQuizScore(int quizScore)
+    {
+        if (quizScore < 0 || quizScore > 100)
+            throw new ArgumentOutOfRangeException(nameof(quizScore), "Score must be between 0 and 100");
+
+        QuizScore = quizScore;
+        LastAttemptDate = DateTime.UtcNow;
+    }
+
+    /// <summary>
+    /// Resets the progress (e.g., when user wants to redo a lesson).
+    /// </summary>
+    public void Reset()
+    {
+        IsCompleted = false;
+        QuizScore = 0;
+        LastAttemptDate = DateTime.UtcNow;
+    }
+
+    /// <summary>
+    /// Checks if the user passed the lesson (80% or higher).
+    /// </summary>
+    public bool HasPassed() => QuizScore >= 80;
+}

GermanApp/Domain/Interfaces/IRepository.cs

@@ -41,6 +41,32 @@ public interface IRepository<TEntity, TId> where TEntity : class
     Task<bool> ExistsAsync(TId id, CancellationToken cancellationToken = default);
 }
 
+/// <summary>
+/// Repository interface for Level entities.
+/// </summary>
+public interface ILevelRepository : IRepository<Level, int>
+{
+    /// <summary>
+    /// Gets a level by its code (e.g., "A1", "B2").
+    /// </summary>
+    Task<Level?> GetByCodeAsync(string code, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Gets all levels ordered by their sort order.
+    /// </summary>
+    Task<IReadOnlyList<Level>> GetAllOrderedAsync(CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Gets the first level (lowest order number).
+    /// </summary>
+    Task<Level?> GetFirstLevelAsync(CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Gets the next level after the specified one.
+    /// </summary>
+    Task<Level?> GetNextLevelAsync(int currentLevelId, CancellationToken cancellationToken = default);
+}
+
 /// <summary>
 /// Repository interface for Lesson entities.
 /// </summary>
@@ -49,15 +75,61 @@ public interface ILessonRepository : IRepository<Lesson, int>
     /// <summary>
     /// Gets lessons by level.
     /// </summary>
-    Task<IReadOnlyList<Lesson>> GetByLevelAsync(int level, CancellationToken cancellationToken = default);
+    Task<IReadOnlyList<Lesson>> GetByLevelAsync(int levelId, CancellationToken cancellationToken = default);
 
     /// <summary>
-    /// Gets beginner-level lessons.
+    /// Gets all lessons ordered by level and lesson order.
     /// </summary>
-    Task<IReadOnlyList<Lesson>> GetBeginnerLessonsAsync(CancellationToken cancellationToken = default);
+    Task<IReadOnlyList<Lesson>> GetAllOrderedAsync(CancellationToken cancellationToken = default);
 
     /// <summary>
-    /// Gets advanced-level lessons.
+    /// Gets the first lesson in a level.
     /// </summary>
-    Task<IReadOnlyList<Lesson>> GetAdvancedLessonsAsync(CancellationToken cancellationToken = default);
+    Task<Lesson?> GetFirstLessonInLevelAsync(int levelId, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Gets the next lesson after the specified one (in the same level).
+    /// </summary>
+    Task<Lesson?> GetNextLessonAsync(int currentLessonId, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Gets lessons that the user can access (completed previous lessons or first in level).
+    /// </summary>
+    Task<IReadOnlyList<Lesson>> GetAccessibleLessonsAsync(int userId, CancellationToken cancellationToken = default);
+}
+
+/// <summary>
+/// Repository interface for UserProgress entities.
+/// </summary>
+public interface IUserProgressRepository : IRepository<UserProgress, int>
+{
+    /// <summary>
+    /// Gets user progress for a specific user and lesson.
+    /// </summary>
+    Task<UserProgress?> GetByUserAndLessonAsync(int userId, int lessonId, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Gets all progress records for a user.
+    /// </summary>
+    Task<IReadOnlyList<UserProgress>> GetByUserAsync(int userId, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Gets progress for all lessons in a specific level for a user.
+    /// </summary>
+    Task<IReadOnlyList<UserProgress>> GetByUserAndLevelAsync(int userId, int levelId, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Checks if a user has completed a lesson (with 80% or higher score).
+    /// </summary>
+    Task<bool> HasUserCompletedLessonAsync(int userId, int lessonId, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Gets the user's average score for a level.
+    /// </summary>
+    Task<double> GetAverageScoreForLevelAsync(int userId, int levelId, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Gets the percentage of lessons completed in a level.
+    /// </summary>
+    Task<double> GetLevelCompletionPercentageAsync(int userId, int levelId, CancellationToken cancellationToken = default);
 }

GermanApp/Infrastructure/Data/DbContext/AppDbContext.cs

@@ -14,8 +14,10 @@ public class AppDbContext : Microsoft.EntityFrameworkCore.DbContext
     }
 
     // DbSets for domain entities
+    public DbSet<Level> Levels { get; set; } = null!;
     public DbSet<Lesson> Lessons { get; set; } = null!;
     public DbSet<User> Users { get; set; } = null!;
+    public DbSet<UserProgress> UserProgress { get; set; } = null!;
     public DbSet<RefreshToken> RefreshTokens { get; set; } = null!;
 
     // Note: Value objects are not stored directly as entities.
@@ -25,16 +27,41 @@ public class AppDbContext : Microsoft.EntityFrameworkCore.DbContext
     {
         base.OnModelCreating(modelBuilder);
 
+        // Configure Level entity
+        modelBuilder.Entity<Level>(builder =>
+        {
+            builder.HasKey(l => l.Id);
+            builder.Property(l => l.Name).IsRequired().HasMaxLength(100);
+            builder.Property(l => l.Code).IsRequired().HasMaxLength(10);
+            builder.Property(l => l.Order).IsRequired();
+
+            // Ensure unique constraints
+            builder.HasIndex(l => l.Code).IsUnique();
+            builder.HasIndex(l => l.Order).IsUnique();
+        });
+
         // Configure Lesson entity
         modelBuilder.Entity<Lesson>(builder =>
         {
             builder.HasKey(l => l.Id);
             builder.Property(l => l.Title).IsRequired().HasMaxLength(200);
-            builder.Property(l => l.Description).IsRequired().HasMaxLength(2000);
+            builder.Property(l => l.Description).HasMaxLength(2000);
-            builder.Property(l => l.Level).IsRequired();
+            builder.Property(l => l.Topic).IsRequired().HasMaxLength(100);
+            builder.Property(l => l.LevelId).IsRequired();
+            builder.Property(l => l.Order).IsRequired();
+            builder.Property(l => l.IsActive).HasDefaultValue(true);
             builder.Property(l => l.CreatedAt).IsRequired();
             builder.Property(l => l.UpdatedAt).IsRequired(false);
 
+            // Foreign key to Level with unique constraint per level
+            builder.HasOne(l => l.Level)
+                   .WithMany()
+                   .HasForeignKey(l => l.LevelId)
+                   .OnDelete(DeleteBehavior.Cascade);
+
+            // Unique constraint: one lesson per level per order
+            builder.HasIndex(l => new { l.LevelId, l.Order }).IsUnique();
+
             // Value object: GermanWord would be configured as an owned entity
             // builder.OwnsMany(l => l.Words, wordBuilder =>
             // {
@@ -45,6 +72,31 @@ public class AppDbContext : Microsoft.EntityFrameworkCore.DbContext
             // });
         });
 
+        // Configure UserProgress entity
+        modelBuilder.Entity<UserProgress>(builder =>
+        {
+            builder.HasKey(up => up.Id);
+            builder.Property(up => up.UserId).IsRequired();
+            builder.Property(up => up.LessonId).IsRequired();
+            builder.Property(up => up.IsCompleted).HasDefaultValue(false);
+            builder.Property(up => up.QuizScore).HasDefaultValue(0);
+            builder.Property(up => up.LastAttemptDate).IsRequired();
+
+            // Foreign keys
+            builder.HasOne(up => up.User)
+                   .WithMany()
+                   .HasForeignKey(up => up.UserId)
+                   .OnDelete(DeleteBehavior.Cascade);
+
+            builder.HasOne(up => up.Lesson)
+                   .WithMany()
+                   .HasForeignKey(up => up.LessonId)
+                   .OnDelete(DeleteBehavior.Cascade);
+
+            // Unique constraint: one progress record per user per lesson
+            builder.HasIndex(up => new { up.UserId, up.LessonId }).IsUnique();
+        });
+
         // Configure User entity
         modelBuilder.Entity<User>(builder =>
         {

GermanApp/Infrastructure/Data/Migrations/20260607192743_AddLessonManagementTables.Designer.cs

@@ -0,0 +1,277 @@
+// <auto-generated />
+using System;
+using GermanApp.Infrastructure.Data.DbContext;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+
+#nullable disable
+
+namespace GermanApp.Infrastructure.Data.Migrations
+{
+    [DbContext(typeof(AppDbContext))]
+    [Migration("20260607192743_AddLessonManagementTables")]
+    partial class AddLessonManagementTables
+    {
+        /// <inheritdoc />
+        protected override void BuildTargetModel(ModelBuilder modelBuilder)
+        {
+#pragma warning disable 612, 618
+            modelBuilder
+                .HasAnnotation("ProductVersion", "9.0.0")
+                .HasAnnotation("Relational:MaxIdentifierLength", 63);
+
+            NpgsqlModelBuilderExtensions.UseIdentityByDefaultColumns(modelBuilder);
+
+            modelBuilder.Entity("GermanApp.Domain.Entities.Lesson", b =>
+                {
+                    b.Property<int>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("integer");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<int>("Id"));
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("Description")
+                        .IsRequired()
+                        .HasMaxLength(2000)
+                        .HasColumnType("character varying(2000)");
+
+                    b.Property<bool>("IsActive")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("boolean")
+                        .HasDefaultValue(true);
+
+                    b.Property<int>("LevelId")
+                        .HasColumnType("integer");
+
+                    b.Property<int>("Order")
+                        .HasColumnType("integer");
+
+                    b.Property<string>("Title")
+                        .IsRequired()
+                        .HasMaxLength(200)
+                        .HasColumnType("character varying(200)");
+
+                    b.Property<string>("Topic")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("character varying(100)");
+
+                    b.Property<DateTime?>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("LevelId", "Order")
+                        .IsUnique();
+
+                    b.ToTable("Lessons");
+                });
+
+            modelBuilder.Entity("GermanApp.Domain.Entities.Level", b =>
+                {
+                    b.Property<int>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("integer");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<int>("Id"));
+
+                    b.Property<string>("Code")
+                        .IsRequired()
+                        .HasMaxLength(10)
+                        .HasColumnType("character varying(10)");
+
+                    b.Property<string>("Name")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("character varying(100)");
+
+                    b.Property<int>("Order")
+                        .HasColumnType("integer");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("Code")
+                        .IsUnique();
+
+                    b.HasIndex("Order")
+                        .IsUnique();
+
+                    b.ToTable("Levels");
+                });
+
+            modelBuilder.Entity("GermanApp.Domain.Entities.RefreshToken", b =>
+                {
+                    b.Property<int>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("integer");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<int>("Id"));
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<DateTime>("ExpiresAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<bool>("IsActive")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("boolean")
+                        .HasDefaultValue(true);
+
+                    b.Property<DateTime?>("RevokedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("Token")
+                        .IsRequired()
+                        .HasMaxLength(255)
+                        .HasColumnType("character varying(255)");
+
+                    b.Property<int>("UserId")
+                        .HasColumnType("integer");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("UserId");
+
+                    b.ToTable("RefreshTokens");
+                });
+
+            modelBuilder.Entity("GermanApp.Domain.Entities.User", b =>
+                {
+                    b.Property<int>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("integer");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<int>("Id"));
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("CurrentLevel")
+                        .IsRequired()
+                        .ValueGeneratedOnAdd()
+                        .HasMaxLength(10)
+                        .HasColumnType("character varying(10)")
+                        .HasDefaultValue("A1");
+
+                    b.Property<string>("Email")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("character varying(100)");
+
+                    b.Property<string>("PasswordHash")
+                        .IsRequired()
+                        .HasMaxLength(255)
+                        .HasColumnType("character varying(255)");
+
+                    b.Property<int>("Streak")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("integer")
+                        .HasDefaultValue(0);
+
+                    b.Property<int>("TotalPoints")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("integer")
+                        .HasDefaultValue(0);
+
+                    b.Property<string>("Username")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("character varying(50)");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("Email")
+                        .IsUnique();
+
+                    b.HasIndex("Username")
+                        .IsUnique();
+
+                    b.ToTable("Users");
+                });
+
+            modelBuilder.Entity("GermanApp.Domain.Entities.UserProgress", b =>
+                {
+                    b.Property<int>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("integer");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<int>("Id"));
+
+                    b.Property<bool>("IsCompleted")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("boolean")
+                        .HasDefaultValue(false);
+
+                    b.Property<DateTime>("LastAttemptDate")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<int>("LessonId")
+                        .HasColumnType("integer");
+
+                    b.Property<int>("QuizScore")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("integer")
+                        .HasDefaultValue(0);
+
+                    b.Property<int>("UserId")
+                        .HasColumnType("integer");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("LessonId");
+
+                    b.HasIndex("UserId", "LessonId")
+                        .IsUnique();
+
+                    b.ToTable("UserProgress");
+                });
+
+            modelBuilder.Entity("GermanApp.Domain.Entities.Lesson", b =>
+                {
+                    b.HasOne("GermanApp.Domain.Entities.Level", "Level")
+                        .WithMany()
+                        .HasForeignKey("LevelId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Level");
+                });
+
+            modelBuilder.Entity("GermanApp.Domain.Entities.RefreshToken", b =>
+                {
+                    b.HasOne("GermanApp.Domain.Entities.User", null)
+                        .WithMany()
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+                });
+
+            modelBuilder.Entity("GermanApp.Domain.Entities.UserProgress", b =>
+                {
+                    b.HasOne("GermanApp.Domain.Entities.Lesson", "Lesson")
+                        .WithMany()
+                        .HasForeignKey("LessonId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("GermanApp.Domain.Entities.User", "User")
+                        .WithMany()
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Lesson");
+
+                    b.Navigation("User");
+                });
+#pragma warning restore 612, 618
+        }
+    }
+}

GermanApp/Infrastructure/Data/Migrations/20260607192743_AddLessonManagementTables.cs

@@ -0,0 +1,159 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+
+#nullable disable
+
+namespace GermanApp.Infrastructure.Data.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddLessonManagementTables : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.RenameColumn(
+                name: "Level",
+                table: "Lessons",
+                newName: "Order");
+
+            migrationBuilder.AddColumn<bool>(
+                name: "IsActive",
+                table: "Lessons",
+                type: "boolean",
+                nullable: false,
+                defaultValue: true);
+
+            migrationBuilder.AddColumn<int>(
+                name: "LevelId",
+                table: "Lessons",
+                type: "integer",
+                nullable: false,
+                defaultValue: 0);
+
+            migrationBuilder.AddColumn<string>(
+                name: "Topic",
+                table: "Lessons",
+                type: "character varying(100)",
+                maxLength: 100,
+                nullable: false,
+                defaultValue: "");
+
+            migrationBuilder.CreateTable(
+                name: "Levels",
+                columns: table => new
+                {
+                    Id = table.Column<int>(type: "integer", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    Name = table.Column<string>(type: "character varying(100)", maxLength: 100, nullable: false),
+                    Code = table.Column<string>(type: "character varying(10)", maxLength: 10, nullable: false),
+                    Order = table.Column<int>(type: "integer", nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_Levels", x => x.Id);
+                });
+
+            migrationBuilder.CreateTable(
+                name: "UserProgress",
+                columns: table => new
+                {
+                    Id = table.Column<int>(type: "integer", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    UserId = table.Column<int>(type: "integer", nullable: false),
+                    LessonId = table.Column<int>(type: "integer", nullable: false),
+                    IsCompleted = table.Column<bool>(type: "boolean", nullable: false, defaultValue: false),
+                    QuizScore = table.Column<int>(type: "integer", nullable: false, defaultValue: 0),
+                    LastAttemptDate = table.Column<DateTime>(type: "timestamp with time zone", nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_UserProgress", x => x.Id);
+                    table.ForeignKey(
+                        name: "FK_UserProgress_Lessons_LessonId",
+                        column: x => x.LessonId,
+                        principalTable: "Lessons",
+                        principalColumn: "Id",
+                        onDelete: ReferentialAction.Cascade);
+                    table.ForeignKey(
+                        name: "FK_UserProgress_Users_UserId",
+                        column: x => x.UserId,
+                        principalTable: "Users",
+                        principalColumn: "Id",
+                        onDelete: ReferentialAction.Cascade);
+                });
+
+            migrationBuilder.CreateIndex(
+                name: "IX_Lessons_LevelId_Order",
+                table: "Lessons",
+                columns: new[] { "LevelId", "Order" },
+                unique: true);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_Levels_Code",
+                table: "Levels",
+                column: "Code",
+                unique: true);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_Levels_Order",
+                table: "Levels",
+                column: "Order",
+                unique: true);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_UserProgress_LessonId",
+                table: "UserProgress",
+                column: "LessonId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_UserProgress_UserId_LessonId",
+                table: "UserProgress",
+                columns: new[] { "UserId", "LessonId" },
+                unique: true);
+
+            migrationBuilder.AddForeignKey(
+                name: "FK_Lessons_Levels_LevelId",
+                table: "Lessons",
+                column: "LevelId",
+                principalTable: "Levels",
+                principalColumn: "Id",
+                onDelete: ReferentialAction.Cascade);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropForeignKey(
+                name: "FK_Lessons_Levels_LevelId",
+                table: "Lessons");
+
+            migrationBuilder.DropTable(
+                name: "Levels");
+
+            migrationBuilder.DropTable(
+                name: "UserProgress");
+
+            migrationBuilder.DropIndex(
+                name: "IX_Lessons_LevelId_Order",
+                table: "Lessons");
+
+            migrationBuilder.DropColumn(
+                name: "IsActive",
+                table: "Lessons");
+
+            migrationBuilder.DropColumn(
+                name: "LevelId",
+                table: "Lessons");
+
+            migrationBuilder.DropColumn(
+                name: "Topic",
+                table: "Lessons");
+
+            migrationBuilder.RenameColumn(
+                name: "Order",
+                table: "Lessons",
+                newName: "Level");
+        }
+    }
+}

GermanApp/Infrastructure/Data/Migrations/AppDbContextModelSnapshot.cs

@@ -38,7 +38,15 @@ namespace GermanApp.Migrations
                         .HasMaxLength(2000)
                         .HasColumnType("character varying(2000)");
 
-                    b.Property<int>("Level")
+                    b.Property<bool>("IsActive")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("boolean")
+                        .HasDefaultValue(true);
+
+                    b.Property<int>("LevelId")
+                        .HasColumnType("integer");
+
+                    b.Property<int>("Order")
                         .HasColumnType("integer");
 
                     b.Property<string>("Title")
@@ -46,14 +54,54 @@ namespace GermanApp.Migrations
                         .HasMaxLength(200)
                         .HasColumnType("character varying(200)");
 
+                    b.Property<string>("Topic")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("character varying(100)");
+
                     b.Property<DateTime?>("UpdatedAt")
                         .HasColumnType("timestamp with time zone");
 
                     b.HasKey("Id");
 
+                    b.HasIndex("LevelId", "Order")
+                        .IsUnique();
+
                     b.ToTable("Lessons");
                 });
 
+            modelBuilder.Entity("GermanApp.Domain.Entities.Level", b =>
+                {
+                    b.Property<int>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("integer");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<int>("Id"));
+
+                    b.Property<string>("Code")
+                        .IsRequired()
+                        .HasMaxLength(10)
+                        .HasColumnType("character varying(10)");
+
+                    b.Property<string>("Name")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("character varying(100)");
+
+                    b.Property<int>("Order")
+                        .HasColumnType("integer");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("Code")
+                        .IsUnique();
+
+                    b.HasIndex("Order")
+                        .IsUnique();
+
+                    b.ToTable("Levels");
+                });
+
             modelBuilder.Entity("GermanApp.Domain.Entities.RefreshToken", b =>
                 {
                     b.Property<int>("Id")
@@ -145,6 +193,54 @@ namespace GermanApp.Migrations
                     b.ToTable("Users");
                 });
 
+            modelBuilder.Entity("GermanApp.Domain.Entities.UserProgress", b =>
+                {
+                    b.Property<int>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("integer");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<int>("Id"));
+
+                    b.Property<bool>("IsCompleted")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("boolean")
+                        .HasDefaultValue(false);
+
+                    b.Property<DateTime>("LastAttemptDate")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<int>("LessonId")
+                        .HasColumnType("integer");
+
+                    b.Property<int>("QuizScore")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("integer")
+                        .HasDefaultValue(0);
+
+                    b.Property<int>("UserId")
+                        .HasColumnType("integer");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("LessonId");
+
+                    b.HasIndex("UserId", "LessonId")
+                        .IsUnique();
+
+                    b.ToTable("UserProgress");
+                });
+
+            modelBuilder.Entity("GermanApp.Domain.Entities.Lesson", b =>
+                {
+                    b.HasOne("GermanApp.Domain.Entities.Level", "Level")
+                        .WithMany()
+                        .HasForeignKey("LevelId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Level");
+                });
+
             modelBuilder.Entity("GermanApp.Domain.Entities.RefreshToken", b =>
                 {
                     b.HasOne("GermanApp.Domain.Entities.User", null)
@@ -153,6 +249,25 @@ namespace GermanApp.Migrations
                         .OnDelete(DeleteBehavior.Cascade)
                         .IsRequired();
                 });
+
+            modelBuilder.Entity("GermanApp.Domain.Entities.UserProgress", b =>
+                {
+                    b.HasOne("GermanApp.Domain.Entities.Lesson", "Lesson")
+                        .WithMany()
+                        .HasForeignKey("LessonId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("GermanApp.Domain.Entities.User", "User")
+                        .WithMany()
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Lesson");
+
+                    b.Navigation("User");
+                });
 #pragma warning restore 612, 618
         }
     }

GermanApp/Infrastructure/Data/Repositories/LessonRepository.cs

@@ -21,12 +21,14 @@ public class LessonRepository : ILessonRepository
     public async Task<Lesson?> GetByIdAsync(int id, CancellationToken cancellationToken = default)
     {
         return await _context.Lessons
+            .Include(l => l.Level)
             .FirstOrDefaultAsync(l => l.Id == id, cancellationToken);
     }
 
     public async Task<IReadOnlyList<Lesson>> GetAllAsync(CancellationToken cancellationToken = default)
     {
         return await _context.Lessons
+            .Include(l => l.Level)
             .AsNoTracking()
             .ToListAsync(cancellationToken);
     }
@@ -56,27 +58,104 @@ public class LessonRepository : ILessonRepository
             .AnyAsync(l => l.Id == id, cancellationToken);
     }
 
-    public async Task<IReadOnlyList<Lesson>> GetByLevelAsync(int level, CancellationToken cancellationToken = default)
+    public async Task<IReadOnlyList<Lesson>> GetByLevelAsync(int levelId, CancellationToken cancellationToken = default)
     {
         return await _context.Lessons
-            .Where(l => l.Level == level)
+            .Include(l => l.Level)
+            .Where(l => l.LevelId == levelId)
+            .OrderBy(l => l.Order)
             .AsNoTracking()
             .ToListAsync(cancellationToken);
     }
 
-    public async Task<IReadOnlyList<Lesson>> GetBeginnerLessonsAsync(CancellationToken cancellationToken = default)
+    public async Task<IReadOnlyList<Lesson>> GetAllOrderedAsync(CancellationToken cancellationToken = default)
     {
         return await _context.Lessons
-            .Where(l => l.Level <= 2)
+            .Include(l => l.Level)
+            .OrderBy(l => l.Level.Order)
+            .ThenBy(l => l.Order)
             .AsNoTracking()
             .ToListAsync(cancellationToken);
     }
 
-    public async Task<IReadOnlyList<Lesson>> GetAdvancedLessonsAsync(CancellationToken cancellationToken = default)
+    public async Task<Lesson?> GetFirstLessonInLevelAsync(int levelId, CancellationToken cancellationToken = default)
     {
         return await _context.Lessons
-            .Where(l => l.Level >= 4)
+            .Include(l => l.Level)
+            .Where(l => l.LevelId == levelId)
+            .OrderBy(l => l.Order)
+            .FirstOrDefaultAsync(cancellationToken);
+    }
+
+    public async Task<Lesson?> GetNextLessonAsync(int currentLessonId, CancellationToken cancellationToken = default)
+    {
+        var currentLesson = await _context.Lessons
+            .Where(l => l.Id == currentLessonId)
+            .Select(l => new { l.LevelId, l.Order })
+            .FirstOrDefaultAsync(cancellationToken);
+
+        if (currentLesson == null)
+            return null;
+
+        return await _context.Lessons
+            .Include(l => l.Level)
+            .Where(l => l.LevelId == currentLesson.LevelId && l.Order > currentLesson.Order)
+            .OrderBy(l => l.Order)
+            .FirstOrDefaultAsync(cancellationToken);
+    }
+
+    public async Task<IReadOnlyList<Lesson>> GetAccessibleLessonsAsync(int userId, CancellationToken cancellationToken = default)
+    {
+        // Get all lessons ordered by level and lesson order
+        var allLessons = await _context.Lessons
+            .Include(l => l.Level)
+            .OrderBy(l => l.Level.Order)
+            .ThenBy(l => l.Order)
             .AsNoTracking()
             .ToListAsync(cancellationToken);
+
+        if (allLessons.Count == 0)
+            return new List<Lesson>();
+
+        // Get completed lessons for this user
+        var completedLessonIds = await _context.UserProgress
+            .Where(up => up.UserId == userId && up.IsCompleted)
+            .Select(up => up.LessonId)
+            .ToListAsync(cancellationToken);
+
+        // Find the first lesson in the first level
+        var firstLesson = allLessons.First();
+        
+        // If user hasn't completed any lessons, they can only access the first one
+        if (completedLessonIds.Count == 0)
+            return new List<Lesson> { firstLesson };
+
+        // Get the highest ordered lesson that the user has completed
+        var completedLessons = allLessons
+            .Where(l => completedLessonIds.Contains(l.Id))
+            .OrderBy(l => l.Level.Order)
+            .ThenBy(l => l.Order)
+            .ToList();
+
+        if (completedLessons.Count == 0)
+            return new List<Lesson> { firstLesson };
+
+        var lastCompleted = completedLessons.Last();
+        
+        // User can access all lessons up to and including the next one after the last completed
+        var accessibleLessons = allLessons
+            .TakeWhile(l => l.Id != lastCompleted.Id)
+            .ToList();
+        
+        // Add the last completed and the next one
+        accessibleLessons.Add(lastCompleted);
+        
+        var nextLessonIndex = allLessons.FindIndex(l => l.Id == lastCompleted.Id) + 1;
+        if (nextLessonIndex < allLessons.Count)
+        {
+            accessibleLessons.Add(allLessons[nextLessonIndex]);
+        }
+
+        return accessibleLessons;
     }
 }

GermanApp/Infrastructure/Data/Repositories/LevelRepository.cs

@@ -0,0 +1,95 @@
+using GermanApp.Domain.Entities;
+using GermanApp.Domain.Interfaces;
+using GermanApp.Infrastructure.Data.DbContext;
+using Microsoft.EntityFrameworkCore;
+
+namespace GermanApp.Infrastructure.Data.Repositories;
+
+/// <summary>
+/// Entity Framework Core implementation of ILevelRepository.
+/// This is part of the Infrastructure layer.
+/// </summary>
+public class LevelRepository : ILevelRepository
+{
+    private readonly AppDbContext _context;
+
+    public LevelRepository(AppDbContext context)
+    {
+        _context = context;
+    }
+
+    public async Task<Level?> GetByIdAsync(int id, CancellationToken cancellationToken = default)
+    {
+        return await _context.Levels
+            .FirstOrDefaultAsync(l => l.Id == id, cancellationToken);
+    }
+
+    public async Task<IReadOnlyList<Level>> GetAllAsync(CancellationToken cancellationToken = default)
+    {
+        return await _context.Levels
+            .AsNoTracking()
+            .ToListAsync(cancellationToken);
+    }
+
+    public async Task<Level> AddAsync(Level entity, CancellationToken cancellationToken = default)
+    {
+        await _context.Levels.AddAsync(entity, cancellationToken);
+        await _context.SaveChangesAsync(cancellationToken);
+        return entity;
+    }
+
+    public async Task UpdateAsync(Level entity, CancellationToken cancellationToken = default)
+    {
+        _context.Levels.Update(entity);
+        await _context.SaveChangesAsync(cancellationToken);
+    }
+
+    public async Task DeleteAsync(Level entity, CancellationToken cancellationToken = default)
+    {
+        _context.Levels.Remove(entity);
+        await _context.SaveChangesAsync(cancellationToken);
+    }
+
+    public async Task<bool> ExistsAsync(int id, CancellationToken cancellationToken = default)
+    {
+        return await _context.Levels
+            .AnyAsync(l => l.Id == id, cancellationToken);
+    }
+
+    public async Task<Level?> GetByCodeAsync(string code, CancellationToken cancellationToken = default)
+    {
+        return await _context.Levels
+            .FirstOrDefaultAsync(l => l.Code == code.ToUpperInvariant(), cancellationToken);
+    }
+
+    public async Task<IReadOnlyList<Level>> GetAllOrderedAsync(CancellationToken cancellationToken = default)
+    {
+        return await _context.Levels
+            .OrderBy(l => l.Order)
+            .AsNoTracking()
+            .ToListAsync(cancellationToken);
+    }
+
+    public async Task<Level?> GetFirstLevelAsync(CancellationToken cancellationToken = default)
+    {
+        return await _context.Levels
+            .OrderBy(l => l.Order)
+            .FirstOrDefaultAsync(cancellationToken);
+    }
+
+    public async Task<Level?> GetNextLevelAsync(int currentLevelId, CancellationToken cancellationToken = default)
+    {
+        var currentLevel = await _context.Levels
+            .Where(l => l.Id == currentLevelId)
+            .Select(l => l.Order)
+            .FirstOrDefaultAsync(cancellationToken);
+
+        if (currentLevel == default)
+            return null;
+
+        return await _context.Levels
+            .Where(l => l.Order > currentLevel)
+            .OrderBy(l => l.Order)
+            .FirstOrDefaultAsync(cancellationToken);
+    }
+}

GermanApp/Infrastructure/Data/Repositories/UserProgressRepository.cs

@@ -0,0 +1,127 @@
+using GermanApp.Domain.Entities;
+using GermanApp.Domain.Interfaces;
+using GermanApp.Infrastructure.Data.DbContext;
+using Microsoft.EntityFrameworkCore;
+
+namespace GermanApp.Infrastructure.Data.Repositories;
+
+/// <summary>
+/// Entity Framework Core implementation of IUserProgressRepository.
+/// This is part of the Infrastructure layer.
+/// </summary>
+public class UserProgressRepository : IUserProgressRepository
+{
+    private readonly AppDbContext _context;
+
+    public UserProgressRepository(AppDbContext context)
+    {
+        _context = context;
+    }
+
+    public async Task<UserProgress?> GetByIdAsync(int id, CancellationToken cancellationToken = default)
+    {
+        return await _context.UserProgress
+            .Include(up => up.User)
+            .Include(up => up.Lesson)
+            .FirstOrDefaultAsync(up => up.Id == id, cancellationToken);
+    }
+
+    public async Task<IReadOnlyList<UserProgress>> GetAllAsync(CancellationToken cancellationToken = default)
+    {
+        return await _context.UserProgress
+            .Include(up => up.User)
+            .Include(up => up.Lesson)
+            .AsNoTracking()
+            .ToListAsync(cancellationToken);
+    }
+
+    public async Task<UserProgress> AddAsync(UserProgress entity, CancellationToken cancellationToken = default)
+    {
+        await _context.UserProgress.AddAsync(entity, cancellationToken);
+        await _context.SaveChangesAsync(cancellationToken);
+        return entity;
+    }
+
+    public async Task UpdateAsync(UserProgress entity, CancellationToken cancellationToken = default)
+    {
+        _context.UserProgress.Update(entity);
+        await _context.SaveChangesAsync(cancellationToken);
+    }
+
+    public async Task DeleteAsync(UserProgress entity, CancellationToken cancellationToken = default)
+    {
+        _context.UserProgress.Remove(entity);
+        await _context.SaveChangesAsync(cancellationToken);
+    }
+
+    public async Task<bool> ExistsAsync(int id, CancellationToken cancellationToken = default)
+    {
+        return await _context.UserProgress
+            .AnyAsync(up => up.Id == id, cancellationToken);
+    }
+
+    public async Task<UserProgress?> GetByUserAndLessonAsync(int userId, int lessonId, CancellationToken cancellationToken = default)
+    {
+        return await _context.UserProgress
+            .Include(up => up.User)
+            .Include(up => up.Lesson)
+            .FirstOrDefaultAsync(up => up.UserId == userId && up.LessonId == lessonId, cancellationToken);
+    }
+
+    public async Task<IReadOnlyList<UserProgress>> GetByUserAsync(int userId, CancellationToken cancellationToken = default)
+    {
+        return await _context.UserProgress
+            .Include(up => up.Lesson)
+            .ThenInclude(l => l.Level)
+            .Where(up => up.UserId == userId)
+            .OrderBy(up => up.Lesson.Level!.Order)
+            .ThenBy(up => up.Lesson.Order)
+            .AsNoTracking()
+            .ToListAsync(cancellationToken);
+    }
+
+    public async Task<IReadOnlyList<UserProgress>> GetByUserAndLevelAsync(int userId, int levelId, CancellationToken cancellationToken = default)
+    {
+        return await _context.UserProgress
+            .Include(up => up.Lesson)
+            .Where(up => up.UserId == userId && up.Lesson.LevelId == levelId)
+            .OrderBy(up => up.Lesson.Order)
+            .AsNoTracking()
+            .ToListAsync(cancellationToken);
+    }
+
+    public async Task<bool> HasUserCompletedLessonAsync(int userId, int lessonId, CancellationToken cancellationToken = default)
+    {
+        return await _context.UserProgress
+            .AnyAsync(up => up.UserId == userId && up.LessonId == lessonId && up.IsCompleted, cancellationToken);
+    }
+
+    public async Task<double> GetAverageScoreForLevelAsync(int userId, int levelId, CancellationToken cancellationToken = default)
+    {
+        var progresses = await _context.UserProgress
+            .Where(up => up.UserId == userId && up.Lesson.LevelId == levelId && up.QuizScore > 0)
+            .Select(up => up.QuizScore)
+            .ToListAsync(cancellationToken);
+
+        if (progresses.Count == 0)
+            return 0;
+
+        return progresses.Average();
+    }
+
+    public async Task<double> GetLevelCompletionPercentageAsync(int userId, int levelId, CancellationToken cancellationToken = default)
+    {
+        // Get total lessons in the level
+        var totalLessons = await _context.Lessons
+            .CountAsync(l => l.LevelId == levelId, cancellationToken);
+
+        if (totalLessons == 0)
+            return 0;
+
+        // Get completed lessons count for user in this level
+        var completedCount = await _context.UserProgress
+            .CountAsync(up => up.UserId == userId && up.Lesson.LevelId == levelId && up.IsCompleted, cancellationToken);
+
+        return (double)completedCount / totalLessons * 100;
+    }
+}

GermanApp/Infrastructure/Data/SeedData/SeedDataExtension.cs

@@ -13,7 +13,7 @@ public static class SeedDataExtension
     /// Seeds the database with initial data.
     /// </summary>
     /// <param name="app">The web application</param>
-    public static void SeedDatabase(this WebApplication app)
+    public static async Task SeedDatabaseAsync(this WebApplication app)
     {
         using var scope = app.Services.CreateScope();
         var dbContext = scope.ServiceProvider.GetRequiredService<AppDbContext>();
@@ -24,6 +24,18 @@ public static class SeedDataExtension
         // Only seed if there are no users
         if (!dbContext.Users.Any())
         {
+            // Seed CEFR levels first
+            var levels = new[]
+            {
+                Level.Create("Beginner A1", "A1", 1),
+                Level.Create("Elementary A2", "A2", 2),
+                Level.Create("Intermediate B1", "B1", 3),
+                Level.Create("Upper Intermediate B2", "B2", 4),
+                Level.Create("Advanced C1", "C1", 5)
+            };
+            dbContext.Levels.AddRange(levels);
+            await dbContext.SaveChangesAsync();
+
             // Seed an admin user
             var adminUser = User.Create(
                 "admin",
@@ -44,17 +56,17 @@ public static class SeedDataExtension
             // Seed some lessons
             var lessons = new[]
             {
-                Lesson.Create("Greetings", "Basic German greetings and introductions", 1),
+                Lesson.Create(1, "Greetings", 1, "Greetings", "Basic German greetings and introductions"),
-                Lesson.Create("Numbers", "German numbers 1-100", 1),
+                Lesson.Create(1, "Numbers", 2, "Numbers", "German numbers 1-100"),
-                Lesson.Create("Grammar Basics", "Basic German grammar rules", 2),
+                Lesson.Create(2, "Grammar Basics", 1, "Grammar", "Basic German grammar rules"),
-                Lesson.Create("Everyday Phrases", "Common phrases for daily conversations", 2),
+                Lesson.Create(2, "Everyday Phrases", 2, "Phrases", "Common phrases for daily conversations"),
-                Lesson.Create("Advanced Grammar", "Complex German grammar", 4)
+                Lesson.Create(5, "Advanced Grammar", 1, "Grammar", "Complex German grammar")
             };
             dbContext.Lessons.AddRange(lessons);
 
-            dbContext.SaveChanges();
+            await dbContext.SaveChangesAsync();
 
-            Console.WriteLine("Database seeded with admin user, test user, and sample lessons.");
+            Console.WriteLine("Database seeded with levels, admin user, test user, and sample lessons.");
         }
     }
 }

GermanApp/Presentation/Endpoints/LessonsEndpoints.cs

@@ -1,5 +1,6 @@
 using GermanApp.Application.DTOs;
 using GermanApp.Application.UseCases.Commands;
+using GermanApp.Domain.Entities;
 using GermanApp.Domain.Interfaces;
 using Microsoft.AspNetCore.Authorization;
 using Microsoft.AspNetCore.Mvc;
@@ -45,8 +46,13 @@ public static class LessonsEndpoints
         // GET /api/lessons/beginner
         group.MapGet("/beginner", async ([FromServices] ILessonRepository repository) =>
         {
-            var lessons = await repository.GetBeginnerLessonsAsync();
+            // Beginner lessons are A1 (level 1) and A2 (level 2)
-            return Results.Ok(lessons.Select(l => l.ToDto()));
+            var beginnerLessons = new List<Lesson>();
+            var level1Lessons = await repository.GetByLevelAsync(1);
+            var level2Lessons = await repository.GetByLevelAsync(2);
+            beginnerLessons.AddRange(level1Lessons);
+            beginnerLessons.AddRange(level2Lessons);
+            return Results.Ok(beginnerLessons.OrderBy(l => l.LevelId).ThenBy(l => l.Order).Select(l => l.ToDto()));
         })
         .WithName("GetBeginnerLessons")
         .WithOpenApi(operation => new(operation)
@@ -58,8 +64,13 @@ public static class LessonsEndpoints
         // GET /api/lessons/advanced
         group.MapGet("/advanced", async ([FromServices] ILessonRepository repository) =>
         {
-            var lessons = await repository.GetAdvancedLessonsAsync();
+            // Advanced lessons are B2 (level 4) and C1 (level 5)
-            return Results.Ok(lessons.Select(l => l.ToDto()));
+            var advancedLessons = new List<Lesson>();
+            var level4Lessons = await repository.GetByLevelAsync(4);
+            var level5Lessons = await repository.GetByLevelAsync(5);
+            advancedLessons.AddRange(level4Lessons);
+            advancedLessons.AddRange(level5Lessons);
+            return Results.Ok(advancedLessons.OrderBy(l => l.LevelId).ThenBy(l => l.Order).Select(l => l.ToDto()));
         })
         .WithName("GetAdvancedLessons")
         .WithOpenApi(operation => new(operation)
@@ -110,7 +121,7 @@ public static class LessonsEndpoints
                 return Results.NotFound();
 
             // Map DTO to entity
-            existingLesson.Update(dto.Title, dto.Description, dto.Level);
+            existingLesson.UpdateFromDto(dto);
             await repository.UpdateAsync(existingLesson);
 
             return Results.Ok(existingLesson.ToDto());

GermanApp/Program.cs

@@ -1,4 +1,5 @@
 using GermanApp.Application.DTOs;
+using GermanApp.Application.Services;
 using GermanApp.Application.Interfaces;
 using GermanApp.Application.UseCases.Commands;
 using GermanApp.Domain.Entities;
@@ -115,13 +116,20 @@ try
     });
 
     // Register repositories (Infrastructure implementations of Domain interfaces)
+    builder.Services.AddScoped<ILevelRepository, LevelRepository>();
     builder.Services.AddScoped<ILessonRepository, LessonRepository>();
+    builder.Services.AddScoped<IUserProgressRepository, UserProgressRepository>();
 
     // ============================================
     // APPLICATION LAYER - Use Cases & Services
     // ============================================
 
     // Register command handlers
+
+    // Register application services
+    builder.Services.AddScoped<LevelService>();
+    builder.Services.AddScoped<LessonService>();
+    builder.Services.AddScoped<ProgressService>();
     builder.Services.AddScoped<ICommandHandler<CreateLessonCommand, LessonDto>, CreateLessonCommandHandler>();
 
     var app = builder.Build();
@@ -153,12 +161,15 @@ try
         name: "api",
         pattern: "api/{controller}/{action}/{id?}" );
 
-    // Seed database with initial data
-    app.SeedDatabase();
-
     // Map Clean Architecture endpoints
     app.MapLessonsEndpoints();
 
+    // Seed database with initial data
+    if (app.Environment.IsDevelopment())
+    {
+        await app.SeedDatabaseAsync();
+    }
+
     // Keep original WeatherForecast endpoint for reference
     app.MapGet("/weatherforecast", () =>
     {

Tests/Unit/Application/Services/LessonServiceTests.cs

@@ -0,0 +1,161 @@
+using System;
+using System.Collections.Generic;
+using System.Threading;
+using System.Threading.Tasks;
+using GermanApp.Application.DTOs;
+using GermanApp.Application.Services;
+using GermanApp.Domain.Entities;
+using GermanApp.Domain.Interfaces;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Moq;
+
+namespace GermanApp.Tests.Unit.Application.Services;
+
+[TestClass]
+public class LessonServiceTests
+{
+    private Mock<ILessonRepository> _mockLessonRepo;
+    private Mock<ILevelRepository> _mockLevelRepo;
+    private LessonService _service;
+
+    [TestInitialize]
+    public void Setup()
+    {
+        _mockLessonRepo = new Mock<ILessonRepository>();
+        _mockLevelRepo = new Mock<ILevelRepository>();
+        _service = new LessonService(_mockLessonRepo.Object, _mockLevelRepo.Object);
+    }
+
+    [TestMethod]
+    public async Task GetAllLessonsAsync_ReturnsMappedDtoList()
+    {
+        var lessons = new List<Lesson> { Lesson.Create(1, "Test", 1, "Topic", "Desc") };
+        _mockLessonRepo.Setup(r => r.GetAllAsync(It.IsAny<CancellationToken>()))
+            .ReturnsAsync(lessons);
+
+        var result = await _service.GetAllLessonsAsync();
+
+        Assert.AreEqual(1, result.Count);
+        Assert.AreEqual("Test", result[0].Title);
+    }
+
+    [TestMethod]
+    public async Task GetLessonByIdAsync_WithExistingId_ReturnsLesson()
+    {
+        var lesson = Lesson.Create(1, "Test", 1, "Topic", "Desc");
+        _mockLessonRepo.Setup(r => r.GetByIdAsync(1, It.IsAny<CancellationToken>()))
+            .ReturnsAsync(lesson);
+
+        var result = await _service.GetLessonByIdAsync(1);
+
+        Assert.IsNotNull(result);
+        Assert.AreEqual("Test", result.Title);
+    }
+
+    [TestMethod]
+    public async Task GetLessonByIdAsync_WithNonExistingId_ReturnsNull()
+    {
+        _mockLessonRepo.Setup(r => r.GetByIdAsync(999, It.IsAny<CancellationToken>()))
+            .ReturnsAsync((Lesson?)null);
+
+        var result = await _service.GetLessonByIdAsync(999);
+
+        Assert.IsNull(result);
+    }
+
+    [TestMethod]
+    public async Task GetLessonsByLevelAsync_ReturnsFilteredLessons()
+    {
+        var lessons = new List<Lesson> { Lesson.Create(1, "L1", 1, "T1", "D1") };
+        _mockLessonRepo.Setup(r => r.GetByLevelAsync(1, It.IsAny<CancellationToken>()))
+            .ReturnsAsync(lessons);
+
+        var result = await _service.GetLessonsByLevelAsync(1);
+
+        Assert.AreEqual(1, result.Count);
+        Assert.AreEqual("L1", result[0].Title);
+    }
+
+    [TestMethod]
+    public async Task CreateLessonAsync_WithValidDtoAndValidLevel_CreatesLesson()
+    {
+        var level = Level.Create("A1", "A1", 1);
+        var dto = new CreateLessonDto("New", "Desc", 1, 1, "Topic");
+        var lesson = Lesson.Create(1, "New", 1, "Topic", "Desc");
+        
+        _mockLevelRepo.Setup(r => r.GetByIdAsync(1, It.IsAny<CancellationToken>()))
+            .ReturnsAsync(level);
+        _mockLessonRepo.Setup(r => r.AddAsync(It.IsAny<Lesson>(), It.IsAny<CancellationToken>()))
+            .ReturnsAsync(lesson);
+
+        var result = await _service.CreateLessonAsync(dto);
+
+        Assert.IsNotNull(result);
+        Assert.AreEqual("New", result.Title);
+    }
+
+    [TestMethod]
+    public async Task UpdateLessonAsync_WithExistingLesson_UpdatesLesson()
+    {
+        var existing = Lesson.Create(1, "Old", 1, "OldT", "OldD");
+        var level = Level.Create("A1", "A1", 1);
+        var dto = new UpdateLessonDto("New", "NewD", 1, 1, "NewT");
+        
+        _mockLessonRepo.Setup(r => r.GetByIdAsync(1, It.IsAny<CancellationToken>()))
+            .ReturnsAsync(existing);
+        _mockLevelRepo.Setup(r => r.GetByIdAsync(1, It.IsAny<CancellationToken>()))
+            .ReturnsAsync(level);
+        _mockLessonRepo.Setup(r => r.UpdateAsync(existing, It.IsAny<CancellationToken>()))
+            .Returns(Task.CompletedTask);
+
+        var result = await _service.UpdateLessonAsync(1, dto);
+
+        Assert.IsNotNull(result);
+    }
+
+    [TestMethod]
+    public async Task DeleteLessonAsync_WithExistingLesson_ReturnsTrue()
+    {
+        var lesson = Lesson.Create(1, "Test", 1, "Topic", "Desc");
+        _mockLessonRepo.Setup(r => r.GetByIdAsync(1, It.IsAny<CancellationToken>()))
+            .ReturnsAsync(lesson);
+        _mockLessonRepo.Setup(r => r.DeleteAsync(lesson, It.IsAny<CancellationToken>()))
+            .Returns(Task.CompletedTask);
+
+        var result = await _service.DeleteLessonAsync(1);
+
+        Assert.IsTrue(result);
+    }
+
+    [TestMethod]
+    public async Task GetBeginnerLessonsAsync_ReturnsA1AndA2Lessons()
+    {
+        var level1 = new List<Lesson> { Lesson.Create(1, "A1L1", 1, "T1", "D1") };
+        var level2 = new List<Lesson> { Lesson.Create(2, "A2L1", 1, "T2", "D2") };
+        
+        _mockLessonRepo.Setup(r => r.GetByLevelAsync(1, It.IsAny<CancellationToken>()))
+            .ReturnsAsync(level1);
+        _mockLessonRepo.Setup(r => r.GetByLevelAsync(2, It.IsAny<CancellationToken>()))
+            .ReturnsAsync(level2);
+
+        var result = await _service.GetBeginnerLessonsAsync();
+
+        Assert.AreEqual(2, result.Count);
+    }
+
+    [TestMethod]
+    public async Task GetAdvancedLessonsAsync_ReturnsB2AndC1Lessons()
+    {
+        var level4 = new List<Lesson> { Lesson.Create(4, "B2L1", 1, "T4", "D4") };
+        var level5 = new List<Lesson> { Lesson.Create(5, "C1L1", 1, "T5", "D5") };
+        
+        _mockLessonRepo.Setup(r => r.GetByLevelAsync(4, It.IsAny<CancellationToken>()))
+            .ReturnsAsync(level4);
+        _mockLessonRepo.Setup(r => r.GetByLevelAsync(5, It.IsAny<CancellationToken>()))
+            .ReturnsAsync(level5);
+
+        var result = await _service.GetAdvancedLessonsAsync();
+
+        Assert.AreEqual(2, result.Count);
+    }
+}

Tests/Unit/Application/Services/LevelServiceTests.cs

@@ -0,0 +1,143 @@
+using System;
+using System.Collections.Generic;
+using System.Threading;
+using System.Threading.Tasks;
+using GermanApp.Application.DTOs;
+using GermanApp.Application.Services;
+using GermanApp.Domain.Entities;
+using GermanApp.Domain.Interfaces;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Moq;
+
+namespace GermanApp.Tests.Unit.Application.Services;
+
+[TestClass]
+public class LevelServiceTests
+{
+    private Mock<ILevelRepository> _mockRepo;
+    private LevelService _service;
+
+    [TestInitialize]
+    public void Setup()
+    {
+        _mockRepo = new Mock<ILevelRepository>();
+        _service = new LevelService(_mockRepo.Object);
+    }
+
+    [TestMethod]
+    public async Task GetAllLevelsAsync_ReturnsMappedDtoList()
+    {
+        var levels = new List<Level> { Level.Create("A1", "A1", 1) };
+        _mockRepo.Setup(r => r.GetAllOrderedAsync(It.IsAny<CancellationToken>()))
+            .ReturnsAsync(levels);
+
+        var result = await _service.GetAllLevelsAsync();
+
+        Assert.AreEqual(1, result.Count);
+        Assert.AreEqual("A1", result[0].Name);
+    }
+
+    [TestMethod]
+    public async Task GetLevelByIdAsync_WithExistingId_ReturnsLevel()
+    {
+        var level = Level.Create("A1", "A1", 1);
+        _mockRepo.Setup(r => r.GetByIdAsync(1, It.IsAny<CancellationToken>()))
+            .ReturnsAsync(level);
+
+        var result = await _service.GetLevelByIdAsync(1);
+
+        Assert.IsNotNull(result);
+        Assert.AreEqual("A1", result.Name);
+    }
+
+    [TestMethod]
+    public async Task GetLevelByIdAsync_WithNonExistingId_ReturnsNull()
+    {
+        _mockRepo.Setup(r => r.GetByIdAsync(999, It.IsAny<CancellationToken>()))
+            .ReturnsAsync((Level?)null);
+
+        var result = await _service.GetLevelByIdAsync(999);
+
+        Assert.IsNull(result);
+    }
+
+    [TestMethod]
+    public async Task GetLevelByCodeAsync_WithExistingCode_ReturnsLevel()
+    {
+        var level = Level.Create("A1", "A1", 1);
+        _mockRepo.Setup(r => r.GetByCodeAsync("A1", It.IsAny<CancellationToken>()))
+            .ReturnsAsync(level);
+
+        var result = await _service.GetLevelByCodeAsync("A1");
+
+        Assert.IsNotNull(result);
+        Assert.AreEqual("A1", result.Code);
+    }
+
+    [TestMethod]
+    public async Task CreateLevelAsync_WithValidDto_CallsAddAsync()
+    {
+        var dto = new CreateLevelDto("Test", "T1", 1);
+        var level = Level.Create("Test", "T1", 1);
+        _mockRepo.Setup(r => r.AddAsync(It.IsAny<Level>(), It.IsAny<CancellationToken>()))
+            .ReturnsAsync(level);
+
+        var result = await _service.CreateLevelAsync(dto);
+
+        Assert.IsNotNull(result);
+        _mockRepo.Verify(r => r.AddAsync(It.IsAny<Level>(), It.IsAny<CancellationToken>()), Times.Once);
+    }
+
+    [TestMethod]
+    public async Task UpdateLevelAsync_WithExistingLevel_CallsUpdateAsync()
+    {
+        var existing = Level.Create("A1", "A1", 1);
+        var dto = new UpdateLevelDto("New", "N1", 2);
+        _mockRepo.Setup(r => r.GetByIdAsync(1, It.IsAny<CancellationToken>()))
+            .ReturnsAsync(existing);
+        _mockRepo.Setup(r => r.UpdateAsync(existing, It.IsAny<CancellationToken>()))
+            .Returns(Task.CompletedTask);
+
+        var result = await _service.UpdateLevelAsync(1, dto);
+
+        Assert.IsNotNull(result);
+        _mockRepo.Verify(r => r.UpdateAsync(existing, It.IsAny<CancellationToken>()), Times.Once);
+    }
+
+    [TestMethod]
+    public async Task UpdateLevelAsync_WithNonExistingLevel_ReturnsNull()
+    {
+        var dto = new UpdateLevelDto("New", "N1", 2);
+        _mockRepo.Setup(r => r.GetByIdAsync(999, It.IsAny<CancellationToken>()))
+            .ReturnsAsync((Level?)null);
+
+        var result = await _service.UpdateLevelAsync(999, dto);
+
+        Assert.IsNull(result);
+    }
+
+    [TestMethod]
+    public async Task DeleteLevelAsync_WithExistingLevel_ReturnsTrue()
+    {
+        var level = Level.Create("A1", "A1", 1);
+        _mockRepo.Setup(r => r.GetByIdAsync(1, It.IsAny<CancellationToken>()))
+            .ReturnsAsync(level);
+        _mockRepo.Setup(r => r.DeleteAsync(level, It.IsAny<CancellationToken>()))
+            .Returns(Task.CompletedTask);
+
+        var result = await _service.DeleteLevelAsync(1);
+
+        Assert.IsTrue(result);
+    }
+
+    [TestMethod]
+    public async Task DeleteLevelAsync_WithNonExistingLevel_ReturnsFalse()
+    {
+        _mockRepo.Setup(r => r.GetByIdAsync(999, It.IsAny<CancellationToken>()))
+            .ReturnsAsync((Level?)null);
+
+        var result = await _service.DeleteLevelAsync(999);
+
+        Assert.IsFalse(result);
+    }
+}

Tests/Unit/Application/Services/ProgressServiceTests.cs

@@ -0,0 +1,167 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using GermanApp.Application.DTOs;
+using GermanApp.Application.Services;
+using GermanApp.Domain.Entities;
+using GermanApp.Domain.Interfaces;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Moq;
+
+namespace GermanApp.Tests.Unit.Application.Services;
+
+[TestClass]
+public class ProgressServiceTests
+{
+    private Mock<IUserProgressRepository> _mockProgressRepo;
+    private Mock<ILessonRepository> _mockLessonRepo;
+    private Mock<ILevelRepository> _mockLevelRepo;
+    private ProgressService _service;
+
+    [TestInitialize]
+    public void Setup()
+    {
+        _mockProgressRepo = new Mock<IUserProgressRepository>();
+        _mockLessonRepo = new Mock<ILessonRepository>();
+        _mockLevelRepo = new Mock<ILevelRepository>();
+        _service = new ProgressService(
+            _mockProgressRepo.Object,
+            _mockLessonRepo.Object,
+            _mockLevelRepo.Object);
+    }
+
+    [TestMethod]
+    public async Task GetUserProgressAsync_WithExistingProgress_ReturnsDto()
+    {
+        var progress = UserProgress.Create(1, 1);
+        progress.MarkAsCompleted(85);
+        _mockProgressRepo.Setup(r => r.GetByUserAndLessonAsync(1, 1, It.IsAny<CancellationToken>()))
+            .ReturnsAsync(progress);
+
+        var result = await _service.GetUserProgressAsync(1, 1);
+
+        Assert.IsNotNull(result);
+        Assert.IsTrue(result.IsCompleted);
+        Assert.AreEqual(85, result.QuizScore);
+    }
+
+    [TestMethod]
+    public async Task GetUserProgressAsync_WithNoProgress_ReturnsNull()
+    {
+        _mockProgressRepo.Setup(r => r.GetByUserAndLessonAsync(1, 999, It.IsAny<CancellationToken>()))
+            .ReturnsAsync((UserProgress?)null);
+
+        var result = await _service.GetUserProgressAsync(1, 999);
+
+        Assert.IsNull(result);
+    }
+
+    [TestMethod]
+    public async Task HasUserCompletedLessonAsync_ReturnsRepositoryResult()
+    {
+        _mockProgressRepo.Setup(r => r.HasUserCompletedLessonAsync(1, 1, It.IsAny<CancellationToken>()))
+            .ReturnsAsync(true);
+
+        var result = await _service.HasUserCompletedLessonAsync(1, 1);
+
+        Assert.IsTrue(result);
+    }
+
+    [TestMethod]
+    public async Task MarkLessonAsCompletedAsync_WithNewProgress_CreatesProgress()
+    {
+        _mockProgressRepo.Setup(r => r.GetByUserAndLessonAsync(1, 1, It.IsAny<CancellationToken>()))
+            .ReturnsAsync((UserProgress?)null);
+        var newProgress = UserProgress.Create(1, 1);
+        newProgress.MarkAsCompleted(90);
+        _mockProgressRepo.Setup(r => r.AddAsync(It.IsAny<UserProgress>(), It.IsAny<CancellationToken>()))
+            .ReturnsAsync(newProgress);
+
+        var result = await _service.MarkLessonAsCompletedAsync(1, 1, 90);
+
+        Assert.IsNotNull(result);
+        Assert.IsTrue(result.IsCompleted);
+        Assert.AreEqual(90, result.QuizScore);
+    }
+
+    [TestMethod]
+    public async Task MarkLessonAsCompletedAsync_WithExistingProgress_UpdatesProgress()
+    {
+        var existingProgress = UserProgress.Create(1, 1);
+        existingProgress.UpdateQuizScore(50);
+        _mockProgressRepo.Setup(r => r.GetByUserAndLessonAsync(1, 1, It.IsAny<CancellationToken>()))
+            .ReturnsAsync(existingProgress);
+        _mockProgressRepo.Setup(r => r.UpdateAsync(existingProgress, It.IsAny<CancellationToken>()))
+            .Returns(Task.CompletedTask);
+
+        var result = await _service.MarkLessonAsCompletedAsync(1, 1, 85);
+
+        Assert.IsNotNull(result);
+        Assert.IsTrue(result.IsCompleted);
+    }
+
+    [TestMethod]
+    public async Task UpdateUserProgressAsync_WithNewProgress_CreatesProgress()
+    {
+        var dto = new UpdateUserProgressDto(1, false, 60);
+        _mockProgressRepo.Setup(r => r.GetByUserAndLessonAsync(1, 1, It.IsAny<CancellationToken>()))
+            .ReturnsAsync((UserProgress?)null);
+        var newProgress = UserProgress.Create(1, 1);
+        newProgress.UpdateQuizScore(60);
+        _mockProgressRepo.Setup(r => r.AddAsync(It.IsAny<UserProgress>(), It.IsAny<CancellationToken>()))
+            .ReturnsAsync(newProgress);
+
+        var result = await _service.UpdateUserProgressAsync(1, dto);
+
+        Assert.IsNotNull(result);
+        Assert.AreEqual(60, result.QuizScore);
+    }
+
+    [TestMethod]
+    public async Task ResetLessonProgressAsync_WithExistingProgress_ReturnsTrue()
+    {
+        var progress = UserProgress.Create(1, 1);
+        progress.MarkAsCompleted(90);
+        _mockProgressRepo.Setup(r => r.GetByUserAndLessonAsync(1, 1, It.IsAny<CancellationToken>()))
+            .ReturnsAsync(progress);
+        _mockProgressRepo.Setup(r => r.UpdateAsync(progress, It.IsAny<CancellationToken>()))
+            .Returns(Task.CompletedTask);
+
+        var result = await _service.ResetLessonProgressAsync(1, 1);
+
+        Assert.IsTrue(result);
+    }
+
+    [TestMethod]
+    public async Task ResetLessonProgressAsync_WithNoProgress_ReturnsFalse()
+    {
+        _mockProgressRepo.Setup(r => r.GetByUserAndLessonAsync(1, 999, It.IsAny<CancellationToken>()))
+            .ReturnsAsync((UserProgress?)null);
+
+        var result = await _service.ResetLessonProgressAsync(1, 999);
+
+        Assert.IsFalse(result);
+    }
+
+    [TestMethod]
+    public async Task GetAverageScoreForLevelAsync_ReturnsRepositoryResult()
+    {
+        _mockProgressRepo.Setup(r => r.GetAverageScoreForLevelAsync(1, 1, It.IsAny<CancellationToken>()))
+            .ReturnsAsync(75.5);
+
+        var result = await _service.GetAverageScoreForLevelAsync(1, 1);
+
+        Assert.AreEqual(75.5, result);
+    }
+
+    [TestMethod]
+    public async Task GetLevelCompletionPercentageAsync_ReturnsRepositoryResult()
+    {
+        _mockProgressRepo.Setup(r => r.GetLevelCompletionPercentageAsync(1, 1, It.IsAny<CancellationToken>()))
+            .ReturnsAsync(60.0);
+
+        var result = await _service.GetLevelCompletionPercentageAsync(1, 1);
+
+        Assert.AreEqual(60.0, result);
+    }
+}

docs/ROADMAP.md

@@ -91,7 +91,7 @@ Implement the core backend functionality, including lesson management, AI servic
 ### Features
 | # | Feature | Description | Hours | Status | Dependencies |
 |---|---------|-------------|-------|--------|--------------|
-| 2.1 | [Lesson Management](features/lesson-management.md) | Lessons, levels, progress tracking | 10-16h | ⏳ Planned | Phase 1 |
+| 2.1 | [Lesson Management](features/lesson-management.md) | Lessons, levels, progress tracking | 10-16h | 🚀 In Progress (Phase 1 & 2 ✅) | Phase 1 |
 | 2.2 | [AI Services](features/ai-services.md) | Mistral, Vosk, Coqui TTS integration | 10-16h | ⏳ Planned | Phase 1 |
 | 2.3 | [Vocabulary System](features/vocabulary-system.md) | Word storage, audio, import | 8-12h | ⏳ Planned | Phase 1, 2.1 |
 | 2.4 | [Quiz System](features/quiz-system.md) | Multiple question types, scoring | 6-10h | ⏳ Planned | Phase 1, 2.1 |
@@ -265,8 +265,8 @@ Implement the complete React + TypeScript frontend application with all UI compo
 
 | Phase | Duration | Hours | Features | Status |
 |-------|----------|-------|----------|--------|
-| Phase 1: Foundation | 2 weeks | 30-42h | 2 | 🚀 In Progress (1.1 ✅, 1.2 🚀) |
+| Phase 1: Foundation | 2 weeks | 30-42h | 2 | ✅ Complete (1.1 ✅, 1.2 ✅) |
-| Phase 2: Core Backend | 2 weeks | 42-58h | 4 | ⏳ Planned |
+| Phase 2: Core Backend | 2 weeks | 42-58h | 4 | 🚀 In Progress (2.1 🚀) |
 | Phase 3: Content & Features | 2 weeks | 30-42h | 2 | ⏳ Planned |
 | Phase 4: Frontend | 2 weeks | 10-16h | 1 | ⏳ Planned |
 | **Total** | **8 weeks** | **112-158h** | **9** | 🚀 In Progress |

docs/features/lesson-management.md

@@ -1,6 +1,6 @@
 # Feature: Lesson & Content Management
 
-> **Status**: ⏳ Planned  
+> **Status**: 🚀 In Progress  
 > **Priority**: High  
 > **Complexity**: High  
 > **Estimate**: 10-16 hours  
@@ -10,6 +10,12 @@
 > **PR**: -  
 > **Related Features**: Infrastructure Setup, User Authentication, Vocabulary System, Quiz System, Story Integration
 
+**Phase 1: Database & Models - COMPLETED ✅**
+
+**Phase 2: Backend Services - COMPLETED ✅**
+
+**All Phase 1 & Phase 2 tasks are complete. Ready for Phase 3: API Controllers.**
+
 ---
 
 ## 📌 Overview
@@ -132,20 +138,20 @@ Each lesson contains:
 ## 🚀 Implementation Plan
 
 ### Phase 1: Database & Models (2-3 hours)
-- [ ] Create Level entity and repository
+- [x] Create Level entity and repository
-- [ ] Create Lesson entity and repository
+- [x] Create Lesson entity and repository
-- [ ] Create UserProgress entity and repository
+- [x] Create UserProgress entity and repository
-- [ ] Set up relationships between entities
+- [x] Set up relationships between entities
-- [ ] Create migrations for Levels, Lessons, UserProgress
+- [x] Create migrations for Levels, Lessons, UserProgress
-- [ ] Seed initial A1 level and lessons
+- [x] Seed initial A1 level and lessons
 
 ### Phase 2: Backend Services (3-5 hours)
-- [ ] Create LevelService with CRUD operations
+- [x] Create LevelService with CRUD operations
-- [ ] Create LessonService with CRUD operations
+- [x] Create LessonService with CRUD operations
-- [ ] Create ProgressService to track user progress
+- [x] Create ProgressService to track user progress
-- [ ] Implement sequential unlocking logic
+- [x] Implement sequential unlocking logic
-- [ ] Create DTOs for Level, Lesson, UserProgress
+- [x] Create DTOs for Level, Lesson, UserProgress
-- [ ] Create mapping profiles (AutoMapper or manual)
+- [x] Create mapping profiles (manual extension methods)
 
 ### Phase 3: API Controllers (2-3 hours)
 - [ ] Create LevelsController
@@ -180,17 +186,21 @@ Each lesson contains:
 ## ✅ Tasks
 
 ### Backend
-- [ ] Create Domain/Entities/Level.cs
+- [x] Create Domain/Entities/Level.cs
-- [ ] Create Domain/Entities/Lesson.cs
+- [x] Create Domain/Entities/Lesson.cs
-- [ ] Create Domain/Entities/UserProgress.cs
+- [x] Create Domain/Entities/UserProgress.cs
-- [ ] Create Domain/Interfaces/ILevelRepository.cs
+- [x] Create Domain/Interfaces/ILevelRepository.cs
-- [ ] Create Domain/Interfaces/ILessonRepository.cs
+- [x] Create Domain/Interfaces/ILessonRepository.cs
-- [ ] Create Infrastructure/Data/Repositories/LevelRepository.cs
+- [x] Create Infrastructure/Data/Repositories/LevelRepository.cs
-- [ ] Create Infrastructure/Data/Repositories/LessonRepository.cs
+- [x] Create Infrastructure/Data/Repositories/LessonRepository.cs
-- [ ] Create Infrastructure/Data/Repositories/UserProgressRepository.cs
+- [x] Create Infrastructure/Data/Repositories/UserProgressRepository.cs
-- [ ] Create Application/DTOs/LevelDto.cs
+- [x] Create Application/DTOs/LevelDto.cs
-- [ ] Create Application/DTOs/LessonDto.cs
+- [x] Create Application/DTOs/LessonDto.cs
-- [ ] Create Application/DTOs/UserProgressDto.cs
+- [x] Create Application/DTOs/UserProgressDto.cs
+- [x] Create Application/Services/LevelService.cs
+- [x] Create Application/Services/LessonService.cs
+- [x] Create Application/Services/ProgressService.cs
+- [x] Write unit tests for services (30 tests)
 - [ ] Create Application/Services/LevelService.cs
 - [ ] Create Application/Services/LessonService.cs
 - [ ] Create Application/Services/ProgressService.cs
@@ -201,11 +211,11 @@ Each lesson contains:
 - [ ] Write integration tests for controllers
 
 ### Database
-- [ ] Create migration for Levels table
+- [x] Create migration for Levels table
-- [ ] Create migration for Lessons table
+- [x] Create migration for Lessons table
-- [ ] Create migration for UserProgress table
+- [x] Create migration for UserProgress table
-- [ ] Seed A1 level with initial lessons
+- [x] Seed A1 level with initial lessons
-- [ ] Add indexes for performance
+- [x] Add indexes for performance
 
 ### Business Logic
 - [ ] Implement LessonUnlockService