feat(backend): Complete Quiz System implementation

- Add Quiz entity with full domain logic (Create, Update, Activate, Deactivate)
- Add QuizQuestion entity updated to use QuizId instead of LessonId
- Add QuizRepository with all CRUD and query methods
- Add QuizQuestionRepository with QuizId-based and LessonId-based (legacy) methods
- Add QuizDto, CreateQuizDto, UpdateQuizDto, QuizWithQuestionsDto, QuizListItemDto
- Add QuizQuestionDto updated with QuizId, LessonId, QuizTitle, Points fields
- Add CreateQuizCommand, UpdateQuizCommand, DeleteQuizCommand, GetQuizWithQuestionsCommand
- Add QuizService with full quiz management (CRUD, activate, deactivate, counts, queries)
- Add QuizQuestionService updated with QuizId-based methods
- Add QuizzesController with comprehensive endpoints (GET, POST, PUT, DELETE)
- Add QuizzesController endpoints for quiz questions (by-quiz, random, active)
- Update QuizQuestionsController with new QuizId-based endpoints (backward compatible)
- Register QuizRepository and QuizService in DI container
- Update IRepository interfaces with QuizId-based methods
- Add SubmitQuizDto for quiz answer submission

Clean Architecture layers maintained:
- Domain: Quiz, QuizQuestion entities with business logic
- Application: DTOs, Commands, Services
- Infrastructure: Repositories, DbContext
- Presentation: Controllers

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

GermanApp/Application/DTOs/QuizDto.cs

@@ -0,0 +1,151 @@
+using GermanApp.Domain.Entities;
+
+namespace GermanApp.Application.DTOs;
+
+/// <summary>
+/// Data Transfer Object for Quiz - used for API responses.
+/// This is a read-only representation of a Quiz entity.
+/// </summary>
+public record QuizDto(
+    int Id,
+    int LessonId,
+    string LessonTitle,
+    string Title,
+    string? Description,
+    int PassingScore,
+    int TimeLimitMinutes,
+    bool ShuffleQuestions,
+    bool IsActive,
+    int QuestionCount,
+    int TotalPoints,
+    DateTime CreatedAt,
+    DateTime? UpdatedAt);
+
+/// <summary>
+/// Data Transfer Object for creating a new Quiz.
+/// </summary>
+public record CreateQuizDto(
+    int LessonId,
+    string Title,
+    string? Description,
+    int PassingScore,
+    int TimeLimitMinutes,
+    bool ShuffleQuestions);
+
+/// <summary>
+/// Data Transfer Object for updating an existing Quiz.
+/// </summary>
+public record UpdateQuizDto(
+    int LessonId,
+    string Title,
+    string? Description,
+    int PassingScore,
+    int TimeLimitMinutes,
+    bool ShuffleQuestions,
+    bool IsActive);
+
+/// <summary>
+/// Data Transfer Object for quiz with its questions.
+/// </summary>
+public record QuizWithQuestionsDto(
+    int Id,
+    int LessonId,
+    string LessonTitle,
+    string Title,
+    string? Description,
+    int PassingScore,
+    int TimeLimitMinutes,
+    bool ShuffleQuestions,
+    bool IsActive,
+    DateTime CreatedAt,
+    DateTime? UpdatedAt,
+    IReadOnlyList<QuizQuestionDto> Questions);
+
+/// <summary>
+/// Data Transfer Object for quiz list item (summary).
+/// </summary>
+public record QuizListItemDto(
+    int Id,
+    int LessonId,
+    string LessonTitle,
+    string Title,
+    bool IsActive,
+    int QuestionCount,
+    DateTime CreatedAt);
+
+/// <summary>
+/// Data Transfer Object for submitting quiz answers.
+/// </summary>
+public record SubmitQuizDto(
+    int QuizId,
+    IReadOnlyList<QuizAnswerDto> Answers);
+
+/// <summary>
+/// Extension methods for mapping between Quiz entity and DTOs.
+/// </summary>
+public static class QuizDtoExtensions
+{
+    public static QuizDto ToDto(this Quiz quiz) => new(
+        quiz.Id,
+        quiz.LessonId,
+        quiz.Lesson?.Title ?? "Unknown",
+        quiz.Title,
+        quiz.Description,
+        quiz.PassingScore,
+        quiz.TimeLimitMinutes,
+        quiz.ShuffleQuestions,
+        quiz.IsActive,
+        quiz.Questions?.Count ?? 0,
+        quiz.Questions?.Sum(q => q.Points) ?? 0,
+        quiz.CreatedAt,
+        quiz.UpdatedAt);
+
+    public static QuizListItemDto ToListItemDto(this Quiz quiz) => new(
+        quiz.Id,
+        quiz.LessonId,
+        quiz.Lesson?.Title ?? "Unknown",
+        quiz.Title,
+        quiz.IsActive,
+        quiz.Questions?.Count ?? 0,
+        quiz.CreatedAt);
+
+    public static QuizWithQuestionsDto ToQuizWithQuestionsDto(this Quiz quiz) => new(
+        quiz.Id,
+        quiz.LessonId,
+        quiz.Lesson?.Title ?? "Unknown",
+        quiz.Title,
+        quiz.Description,
+        quiz.PassingScore,
+        quiz.TimeLimitMinutes,
+        quiz.ShuffleQuestions,
+        quiz.IsActive,
+        quiz.CreatedAt,
+        quiz.UpdatedAt,
+        quiz.Questions?.OrderBy(q => q.Order).Select(q => q.ToDto()).ToList() ?? new List<QuizQuestionDto>());
+
+    public static Quiz ToEntity(this CreateQuizDto dto) =>
+        Quiz.Create(
+            dto.LessonId,
+            dto.Title,
+            dto.Description,
+            dto.PassingScore,
+            dto.TimeLimitMinutes);
+
+    public static void UpdateFromDto(this Quiz quiz, UpdateQuizDto dto)
+    {
+        quiz.UpdateLesson(dto.LessonId);
+        quiz.UpdateTitle(dto.Title);
+        quiz.UpdateDescription(dto.Description);
+        quiz.UpdatePassingScore(dto.PassingScore);
+        quiz.UpdateTimeLimit(dto.TimeLimitMinutes);
+        quiz.UpdateShuffleQuestions(dto.ShuffleQuestions);
+        
+        if (dto.IsActive != quiz.IsActive)
+        {
+            if (dto.IsActive)
+                quiz.Activate();
+            else
+                quiz.Deactivate();
+        }
+    }
+}

GermanApp/Application/DTOs/QuizQuestionDto.cs

@@ -8,11 +8,14 @@ namespace GermanApp.Application.DTOs;
 /// </summary>
 public record QuizQuestionDto(
     int Id,
+    int QuizId,
     int LessonId,
+    string QuizTitle,
     string LessonTitle,
     string QuestionText,
     QuestionType Type,
     string? CorrectAnswer,
+    int Points,
     int Difficulty,
     int Order,
     bool IsActive,
@@ -24,10 +27,11 @@ public record QuizQuestionDto(
 /// Data Transfer Object for creating a new QuizQuestion.
 /// </summary>
 public record CreateQuizQuestionDto(
-    int LessonId,
+    int QuizId,
     string QuestionText,
     QuestionType Type,
     string? CorrectAnswer,
+    int Points,
     int Difficulty,
     int Order,
     IReadOnlyList<CreateQuizOptionDto>? Options);
@@ -36,10 +40,11 @@ public record CreateQuizQuestionDto(
 /// Data Transfer Object for updating an existing QuizQuestion.
 /// </summary>
 public record UpdateQuizQuestionDto(
-    int LessonId,
+    int QuizId,
     string QuestionText,
     QuestionType Type,
     string? CorrectAnswer,
+    int Points,
     int Difficulty,
     int Order,
     bool IsActive,
@@ -77,9 +82,11 @@ public record UpdateQuizOptionDto(
 /// </summary>
 public record QuizQuestionWithAnswerDto(
     int QuizQuestionId,
+    int QuizId,
     int LessonId,
     string QuestionText,
     QuestionType Type,
+    int Points,
     IReadOnlyList<QuizOptionDto> Options,
     string? UserAnswer,
     bool IsCorrect);
@@ -88,7 +95,7 @@ public record QuizQuestionWithAnswerDto(
 /// Data Transfer Object for submitting quiz answers.
 /// </summary>
 public record SubmitQuizAnswersDto(
-    int LessonId,
+    int QuizId,
     IReadOnlyList<QuizAnswerDto> Answers);
 
 /// <summary>
@@ -103,9 +110,12 @@ public record QuizAnswerDto(
 /// Data Transfer Object for quiz result.
 /// </summary>
 public record QuizResultDto(
+    int QuizId,
     int LessonId,
+    string QuizTitle,
     int TotalQuestions,
-    int CorrectAnswers,
+    int TotalPoints,
+    int ScorePoints,
     double ScorePercentage,
     bool Passed,
     TimeSpan TimeTaken,
@@ -118,6 +128,7 @@ public record QuizQuestionResultDto(
     int QuizQuestionId,
     string QuestionText,
     QuestionType Type,
+    int Points,
     bool IsCorrect,
     string? CorrectAnswer,
     string? UserAnswer);
@@ -129,11 +140,14 @@ public static class QuizQuestionDtoExtensions
 {
     public static QuizQuestionDto ToDto(this QuizQuestion quizQuestion) => new(
         quizQuestion.Id,
-        quizQuestion.LessonId,
+        quizQuestion.QuizId,
-        quizQuestion.Lesson?.Title ?? "Unknown",
+        quizQuestion.Quiz?.LessonId ?? 0,
+        quizQuestion.Quiz?.Title ?? "Unknown",
+        quizQuestion.Quiz?.Lesson?.Title ?? "Unknown",
         quizQuestion.QuestionText,
         quizQuestion.Type,
         quizQuestion.CorrectAnswer,
+        quizQuestion.Points,
         quizQuestion.Difficulty,
         quizQuestion.Order,
         quizQuestion.IsActive,
@@ -143,19 +157,21 @@ public static class QuizQuestionDtoExtensions
 
     public static QuizQuestion ToEntity(this CreateQuizQuestionDto dto) =>
         QuizQuestion.Create(
-            dto.LessonId,
+            dto.QuizId,
             dto.QuestionText,
             dto.Type,
             dto.CorrectAnswer ?? string.Empty,
+            dto.Points,
             dto.Difficulty,
             dto.Order);
 
     public static void UpdateFromDto(this QuizQuestion quizQuestion, UpdateQuizQuestionDto dto)
     {
-        quizQuestion.UpdateLesson(dto.LessonId);
+        quizQuestion.UpdateQuiz(dto.QuizId);
         quizQuestion.UpdateQuestionText(dto.QuestionText);
         quizQuestion.UpdateType(dto.Type);
         quizQuestion.UpdateCorrectAnswer(dto.CorrectAnswer ?? string.Empty);
+        quizQuestion.UpdatePoints(dto.Points);
         quizQuestion.UpdateDifficulty(dto.Difficulty);
         quizQuestion.UpdateOrder(dto.Order);
         

GermanApp/Application/Services/QuizQuestionService.cs

@@ -1,5 +1,6 @@
 using GermanApp.Application.DTOs;
 using GermanApp.Domain.Entities;
+using GermanApp.Domain.Exceptions;
 using GermanApp.Domain.Interfaces;
 
 namespace GermanApp.Application.Services;
@@ -12,15 +13,18 @@ public class QuizQuestionService
 {
     private readonly IQuizQuestionRepository _quizQuestionRepository;
     private readonly IQuizOptionRepository _quizOptionRepository;
+    private readonly IQuizRepository _quizRepository;
     private readonly ILessonRepository _lessonRepository;
 
     public QuizQuestionService(
         IQuizQuestionRepository quizQuestionRepository,
         IQuizOptionRepository quizOptionRepository,
+        IQuizRepository quizRepository,
         ILessonRepository lessonRepository)
     {
         _quizQuestionRepository = quizQuestionRepository;
         _quizOptionRepository = quizOptionRepository;
+        _quizRepository = quizRepository;
         _lessonRepository = lessonRepository;
     }
 
@@ -92,13 +96,13 @@ public class QuizQuestionService
     /// </summary>
     public virtual async Task<QuizQuestionDto> CreateQuizQuestionAsync(CreateQuizQuestionDto dto, CancellationToken cancellationToken = default)
     {
-        // Validate that the lesson exists
+        // Validate that the quiz exists
-        var lesson = await _lessonRepository.GetByIdAsync(dto.LessonId, cancellationToken);
+        var quiz = await _quizRepository.GetByIdAsync(dto.QuizId, cancellationToken);
-        if (lesson == null)
+        if (quiz == null)
-            throw new ArgumentException("Lesson does not exist");
+            throw new NotFoundException("Quiz does not exist");
 
-        // Validate question order uniqueness within the lesson
+        // Validate question order uniqueness within the quiz
-        await ValidateQuestionOrderUniquenessAsync(0, dto.LessonId, dto.Order, cancellationToken);
+        await ValidateQuestionOrderUniquenessAsync(0, dto.QuizId, dto.Order, cancellationToken);
 
         // Create the question
         var question = dto.ToEntity();
@@ -128,13 +132,13 @@ public class QuizQuestionService
         if (question == null)
             return null;
 
-        // Validate that the lesson exists
+        // Validate that the quiz exists
-        var lesson = await _lessonRepository.GetByIdAsync(dto.LessonId, cancellationToken);
+        var quiz = await _quizRepository.GetByIdAsync(dto.QuizId, cancellationToken);
-        if (lesson == null)
+        if (quiz == null)
-            throw new ArgumentException("Lesson does not exist");
+            throw new NotFoundException("Quiz does not exist");
 
-        // Validate question order uniqueness within the lesson
+        // Validate question order uniqueness within the quiz
-        await ValidateQuestionOrderUniquenessAsync(id, dto.LessonId, dto.Order, cancellationToken);
+        await ValidateQuestionOrderUniquenessAsync(id, dto.QuizId, dto.Order, cancellationToken);
 
         // Update the question
         question.UpdateFromDto(dto);
@@ -160,13 +164,13 @@ public class QuizQuestionService
     }
 
     /// <summary>
-    /// Validates that the question order is unique within its lesson.
+    /// Validates that the question order is unique within its quiz.
     /// </summary>
-    private async Task ValidateQuestionOrderUniquenessAsync(int excludeQuestionId, int lessonId, int order, CancellationToken cancellationToken)
+    private async Task ValidateQuestionOrderUniquenessAsync(int excludeQuestionId, int quizId, int order, CancellationToken cancellationToken)
     {
-        var exists = await _quizQuestionRepository.OrderExistsInLessonAsync(lessonId, order, excludeQuestionId, cancellationToken);
+        var exists = await _quizQuestionRepository.OrderExistsInQuizAsync(quizId, order, excludeQuestionId, cancellationToken);
         if (exists)
-            throw new ArgumentException("A quiz question with this order already exists in the specified lesson");
+            throw new ValidationException("A quiz question with this order already exists in the specified quiz");
     }
 
     /// <summary>
@@ -277,18 +281,21 @@ public class QuizQuestionService
     }
 
     /// <summary>
-    /// Submits quiz answers and returns the result.
+    /// Submits quiz answers for a specific quiz and returns the result.
     /// </summary>
-    public virtual async Task<QuizResultDto> SubmitQuizAnswersAsync(int userId, SubmitQuizAnswersDto dto, CancellationToken cancellationToken = default)
+    public virtual async Task<QuizResultDto> SubmitQuizAnswersForQuizAsync(int userId, SubmitQuizDto dto, CancellationToken cancellationToken = default)
     {
-        var questions = await _quizQuestionRepository.GetByLessonAsync(dto.LessonId, cancellationToken);
+        var quiz = await _quizRepository.GetWithQuestionsAsync(dto.QuizId, cancellationToken);
-        var questionDictionary = questions.ToDictionary(q => q.Id);
+        if (quiz == null)
+            throw new NotFoundException("Quiz does not exist");
 
+        var questions = quiz.Questions?.Where(q => q.IsActive).OrderBy(q => q.Order).ToList() ?? new List<QuizQuestion>();
         var totalQuestions = questions.Count;
-        var correctAnswers = 0;
+        var totalPoints = questions.Sum(q => q.Points);
+        var scorePoints = 0;
         var questionResults = new List<QuizQuestionResultDto>();
 
-        // Get user's answers
+        // Get user's answers (using QuizAnswerDto which has the same fields as SubmitAnswerDto)
         var userAnswers = dto.Answers.ToDictionary(a => a.QuizQuestionId);
 
         foreach (var question in questions)
@@ -299,7 +306,7 @@ public class QuizQuestionService
 
             if (userAnswers.TryGetValue(question.Id, out var userAnswer))
             {
-                userAnswerText = userAnswer?.AnswerText ?? string.Empty;
+                userAnswerText = userAnswer.AnswerText ?? string.Empty;
 
                 switch (question.Type)
                 {
@@ -341,7 +348,7 @@ public class QuizQuestionService
                         // Case-insensitive comparison with trimming
                         if (!string.IsNullOrEmpty(userAnswerText) && !string.IsNullOrEmpty(correctAnswer))
                         {
-                            isCorrect = userAnswerText.Equals(correctAnswer, StringComparison.OrdinalIgnoreCase);
+                            isCorrect = userAnswerText.Trim().Equals(correctAnswer.Trim(), StringComparison.OrdinalIgnoreCase);
                         }
                         break;
 
@@ -353,30 +360,47 @@ public class QuizQuestionService
             }
 
             if (isCorrect)
-                correctAnswers++;
+                scorePoints += question.Points;
 
             questionResults.Add(new QuizQuestionResultDto(
                 question.Id,
                 question.QuestionText,
                 question.Type,
+                question.Points,
                 isCorrect,
                 correctAnswer,
                 userAnswerText));
         }
 
-        var scorePercentage = totalQuestions > 0 ? (double)correctAnswers / totalQuestions * 100 : 0;
+        var scorePercentage = totalPoints > 0 ? (double)scorePoints / totalPoints * 100 : 0;
-        var passed = scorePercentage >= 80; // Passing score is 80%
+        var passed = quiz.IsPassed(scorePercentage);
 
         return new QuizResultDto(
-            dto.LessonId,
+            quiz.Id,
+            quiz.LessonId,
+            quiz.Title,
             totalQuestions,
-            correctAnswers,
+            totalPoints,
+            scorePoints,
             scorePercentage,
             passed,
             TimeSpan.Zero, // Would be calculated based on actual time taken
             questionResults);
     }
 
+    /// <summary>
+    /// Submits quiz answers and returns the result (legacy - converts SubmitQuizAnswersDto to SubmitQuizDto).
+    /// </summary>
+    public virtual async Task<QuizResultDto> SubmitQuizAnswersAsync(int userId, SubmitQuizAnswersDto dto, CancellationToken cancellationToken = default)
+    {
+        // Convert legacy DTO to new format
+        // SubmitQuizAnswersDto has QuizId and Answers (IReadOnlyList<QuizAnswerDto>)
+        // SubmitQuizDto has QuizId and Answers (IReadOnlyList<QuizAnswerDto>)
+        // They're the same, so just create a new SubmitQuizDto
+        var newDto = new SubmitQuizDto(dto.QuizId, dto.Answers);
+        return await SubmitQuizAnswersForQuizAsync(userId, newDto, cancellationToken);
+    }
+
     /// <summary>
     /// Gets the number of quiz questions for a lesson.
     /// </summary>
@@ -417,4 +441,43 @@ public class QuizQuestionService
 
         return distribution;
     }
+
+    // ============================================
+    // Quiz-based methods (QuizId)
+    // ============================================
+
+    /// <summary>
+    /// Gets quiz questions by quiz ID.
+    /// </summary>
+    public virtual async Task<IReadOnlyList<QuizQuestionDto>> GetQuizQuestionsByQuizAsync(int quizId, CancellationToken cancellationToken = default)
+    {
+        var questions = await _quizQuestionRepository.GetByQuizAsync(quizId, cancellationToken);
+        return questions.Select(q => q.ToDto()).ToList();
+    }
+
+    /// <summary>
+    /// Gets active quiz questions by quiz ID.
+    /// </summary>
+    public virtual async Task<IReadOnlyList<QuizQuestionDto>> GetActiveQuizQuestionsByQuizAsync(int quizId, CancellationToken cancellationToken = default)
+    {
+        var questions = await _quizQuestionRepository.GetActiveByQuizAsync(quizId, cancellationToken);
+        return questions.Select(q => q.ToDto()).ToList();
+    }
+
+    /// <summary>
+    /// Gets a random set of quiz questions for a quiz.
+    /// </summary>
+    public virtual async Task<IReadOnlyList<QuizQuestionDto>> GetRandomQuizQuestionsForQuizAsync(int quizId, int count, CancellationToken cancellationToken = default)
+    {
+        var questions = await _quizQuestionRepository.GetRandomQuestionsForQuizAsync(quizId, count, cancellationToken);
+        return questions.Select(q => q.ToDto()).ToList();
+    }
+
+    /// <summary>
+    /// Gets the total points for a quiz.
+    /// </summary>
+    public virtual async Task<int> GetTotalPointsForQuizAsync(int quizId, CancellationToken cancellationToken = default)
+    {
+        return await _quizQuestionRepository.GetTotalPointsForQuizAsync(quizId, cancellationToken);
+    }
 }

GermanApp/Application/Services/QuizService.cs

@@ -0,0 +1,273 @@
+using GermanApp.Application.DTOs;
+using GermanApp.Domain.Entities;
+using GermanApp.Domain.Exceptions;
+using GermanApp.Domain.Interfaces;
+
+namespace GermanApp.Application.Services;
+
+/// <summary>
+/// Application service for managing quizzes.
+/// This is part of the Application layer.
+/// </summary>
+public class QuizService
+{
+    private readonly IQuizRepository _quizRepository;
+    private readonly IQuizQuestionRepository _quizQuestionRepository;
+    private readonly IQuizOptionRepository _quizOptionRepository;
+    private readonly ILessonRepository _lessonRepository;
+
+    public QuizService(
+        IQuizRepository quizRepository,
+        IQuizQuestionRepository quizQuestionRepository,
+        IQuizOptionRepository quizOptionRepository,
+        ILessonRepository lessonRepository)
+    {
+        _quizRepository = quizRepository;
+        _quizQuestionRepository = quizQuestionRepository;
+        _quizOptionRepository = quizOptionRepository;
+        _lessonRepository = lessonRepository;
+    }
+
+    /// <summary>
+    /// Gets all quizzes.
+    /// </summary>
+    public virtual async Task<IReadOnlyList<QuizDto>> GetAllQuizzesAsync(CancellationToken cancellationToken = default)
+    {
+        var quizzes = await _quizRepository.GetAllOrderedAsync(cancellationToken);
+        return quizzes.Select(q => q.ToDto()).ToList();
+    }
+
+    /// <summary>
+    /// Gets all quizzes as list items (summary).
+    /// </summary>
+    public virtual async Task<IReadOnlyList<QuizListItemDto>> GetAllQuizListItemsAsync(CancellationToken cancellationToken = default)
+    {
+        var quizzes = await _quizRepository.GetAllOrderedAsync(cancellationToken);
+        return quizzes.Select(q => q.ToListItemDto()).ToList();
+    }
+
+    /// <summary>
+    /// Gets a quiz by its ID.
+    /// </summary>
+    public virtual async Task<QuizDto?> GetQuizByIdAsync(int id, CancellationToken cancellationToken = default)
+    {
+        var quiz = await _quizRepository.GetByIdAsync(id, cancellationToken);
+        return quiz?.ToDto();
+    }
+
+    /// <summary>
+    /// Gets a quiz with its questions by ID.
+    /// </summary>
+    public virtual async Task<QuizWithQuestionsDto?> GetQuizWithQuestionsAsync(int id, CancellationToken cancellationToken = default)
+    {
+        var quiz = await _quizRepository.GetWithQuestionsAsync(id, cancellationToken);
+        return quiz?.ToQuizWithQuestionsDto();
+    }
+
+    /// <summary>
+    /// Gets quizzes by lesson ID.
+    /// </summary>
+    public virtual async Task<IReadOnlyList<QuizDto>> GetQuizzesByLessonAsync(int lessonId, CancellationToken cancellationToken = default)
+    {
+        var quizzes = await _quizRepository.GetByLessonAsync(lessonId, cancellationToken);
+        return quizzes.Select(q => q.ToDto()).ToList();
+    }
+
+    /// <summary>
+    /// Gets active quizzes by lesson ID.
+    /// </summary>
+    public virtual async Task<IReadOnlyList<QuizDto>> GetActiveQuizzesByLessonAsync(int lessonId, CancellationToken cancellationToken = default)
+    {
+        var quizzes = await _quizRepository.GetActiveByLessonAsync(lessonId, cancellationToken);
+        return quizzes.Select(q => q.ToDto()).ToList();
+    }
+
+    /// <summary>
+    /// Gets the first quiz for a lesson.
+    /// </summary>
+    public virtual async Task<QuizDto?> GetFirstQuizByLessonAsync(int lessonId, CancellationToken cancellationToken = default)
+    {
+        var quiz = await _quizRepository.GetFirstByLessonAsync(lessonId, cancellationToken);
+        return quiz?.ToDto();
+    }
+
+    /// <summary>
+    /// Creates a new quiz.
+    /// </summary>
+    public virtual async Task<QuizDto> CreateQuizAsync(CreateQuizDto dto, CancellationToken cancellationToken = default)
+    {
+        // Validate that the lesson exists
+        var lesson = await _lessonRepository.GetByIdAsync(dto.LessonId, cancellationToken);
+        if (lesson == null)
+            throw new NotFoundException("Lesson does not exist");
+
+        // Validate business rules
+        if (dto.PassingScore < 0 || dto.PassingScore > 100)
+        {
+            throw new ValidationException("Passing score must be between 0 and 100");
+        }
+
+        if (dto.TimeLimitMinutes < 0)
+        {
+            throw new ValidationException("Time limit cannot be negative");
+        }
+
+        // Convert DTO to domain entity
+        var quiz = dto.ToEntity();
+
+        // Add to repository
+        var createdQuiz = await _quizRepository.AddAsync(quiz, cancellationToken);
+
+        // Return DTO representation
+        return createdQuiz.ToDto();
+    }
+
+    /// <summary>
+    /// Updates an existing quiz.
+    /// </summary>
+    public virtual async Task<QuizDto?> UpdateQuizAsync(int id, UpdateQuizDto dto, CancellationToken cancellationToken = default)
+    {
+        var quiz = await _quizRepository.GetByIdAsync(id, cancellationToken);
+        if (quiz == null)
+            return null;
+
+        // Validate that the lesson exists
+        var lesson = await _lessonRepository.GetByIdAsync(dto.LessonId, cancellationToken);
+        if (lesson == null)
+            throw new NotFoundException("Lesson does not exist");
+
+        // Validate business rules
+        if (dto.PassingScore < 0 || dto.PassingScore > 100)
+        {
+            throw new ValidationException("Passing score must be between 0 and 100");
+        }
+
+        if (dto.TimeLimitMinutes < 0)
+        {
+            throw new ValidationException("Time limit cannot be negative");
+        }
+
+        // Update the quiz
+        quiz.UpdateFromDto(dto);
+        await _quizRepository.UpdateAsync(quiz, cancellationToken);
+
+        // Reload and return
+        var updatedQuiz = await _quizRepository.GetByIdAsync(id, cancellationToken);
+        return updatedQuiz?.ToDto();
+    }
+
+    /// <summary>
+    /// Deletes a quiz by its ID.
+    /// </summary>
+    public virtual async Task<bool> DeleteQuizAsync(int id, CancellationToken cancellationToken = default)
+    {
+        var quiz = await _quizRepository.GetByIdAsync(id, cancellationToken);
+        if (quiz == null)
+            return false;
+
+        // First, delete all options for all questions in this quiz
+        var questions = await _quizQuestionRepository.GetByQuizAsync(id, cancellationToken);
+        foreach (var question in questions)
+        {
+            await _quizOptionRepository.DeleteByQuestionAsync(question.Id, cancellationToken);
+        }
+        
+        // Then delete all questions for this quiz
+        foreach (var question in questions)
+        {
+            await _quizQuestionRepository.DeleteAsync(question, cancellationToken);
+        }
+        
+        // Finally, delete the quiz itself
+        await _quizRepository.DeleteAsync(quiz, cancellationToken);
+        return true;
+    }
+
+    /// <summary>
+    /// Checks if a quiz exists for a lesson.
+    /// </summary>
+    public virtual async Task<bool> ExistsByLessonAsync(int lessonId, CancellationToken cancellationToken = default)
+    {
+        return await _quizRepository.ExistsByLessonAsync(lessonId, cancellationToken);
+    }
+
+    /// <summary>
+    /// Checks if a quiz exists by ID.
+    /// </summary>
+    public virtual async Task<bool> ExistsAsync(int id, CancellationToken cancellationToken = default)
+    {
+        return await _quizRepository.ExistsAsync(id, cancellationToken);
+    }
+
+    /// <summary>
+    /// Gets the total number of quizzes.
+    /// </summary>
+    public virtual async Task<int> GetTotalQuizCountAsync(CancellationToken cancellationToken = default)
+    {
+        var quizzes = await _quizRepository.GetAllAsync(cancellationToken);
+        return quizzes.Count;
+    }
+
+    /// <summary>
+    /// Gets the total number of quizzes for a lesson.
+    /// </summary>
+    public virtual async Task<int> GetQuizCountByLessonAsync(int lessonId, CancellationToken cancellationToken = default)
+    {
+        var quizzes = await _quizRepository.GetByLessonAsync(lessonId, cancellationToken);
+        return quizzes.Count;
+    }
+
+    /// <summary>
+    /// Gets quizzes by passing score range.
+    /// </summary>
+    public virtual async Task<IReadOnlyList<QuizDto>> GetQuizzesByPassingScoreRangeAsync(int minScore, int maxScore, CancellationToken cancellationToken = default)
+    {
+        var quizzes = await _quizRepository.GetAllAsync(cancellationToken);
+        return quizzes.Where(q => q.PassingScore >= minScore && q.PassingScore <= maxScore)
+                       .Select(q => q.ToDto())
+                       .ToList();
+    }
+
+    /// <summary>
+    /// Gets active quizzes.
+    /// </summary>
+    public virtual async Task<IReadOnlyList<QuizDto>> GetActiveQuizzesAsync(CancellationToken cancellationToken = default)
+    {
+        var quizzes = await _quizRepository.GetAllAsync(cancellationToken);
+        return quizzes.Where(q => q.IsActive)
+                       .Select(q => q.ToDto())
+                       .ToList();
+    }
+
+    /// <summary>
+    /// Activates a quiz.
+    /// </summary>
+    public virtual async Task<QuizDto?> ActivateQuizAsync(int id, CancellationToken cancellationToken = default)
+    {
+        var quiz = await _quizRepository.GetByIdAsync(id, cancellationToken);
+        if (quiz == null)
+            return null;
+
+        quiz.Activate();
+        await _quizRepository.UpdateAsync(quiz, cancellationToken);
+
+        var updatedQuiz = await _quizRepository.GetByIdAsync(id, cancellationToken);
+        return updatedQuiz?.ToDto();
+    }
+
+    /// <summary>
+    /// Deactivates a quiz.
+    /// </summary>
+    public virtual async Task<QuizDto?> DeactivateQuizAsync(int id, CancellationToken cancellationToken = default)
+    {
+        var quiz = await _quizRepository.GetByIdAsync(id, cancellationToken);
+        if (quiz == null)
+            return null;
+
+        quiz.Deactivate();
+        await _quizRepository.UpdateAsync(quiz, cancellationToken);
+
+        var updatedQuiz = await _quizRepository.GetByIdAsync(id, cancellationToken);
+        return updatedQuiz?.ToDto();
+    }
+}

GermanApp/Application/UseCases/Commands/CreateQuizCommand.cs

@@ -0,0 +1,162 @@
+using GermanApp.Application.DTOs;
+using GermanApp.Domain.Entities;
+using GermanApp.Domain.Exceptions;
+using GermanApp.Domain.Interfaces;
+
+namespace GermanApp.Application.UseCases.Commands;
+
+/// <summary>
+/// Command for creating a new quiz.
+/// This follows the CQRS pattern - commands represent write operations.
+/// </summary>
+public record CreateQuizCommand(CreateQuizDto QuizData) : ICommand<QuizDto>;
+
+/// <summary>
+/// Handler for the CreateQuizCommand.
+/// </summary>
+public class CreateQuizCommandHandler : ICommandHandler<CreateQuizCommand, QuizDto>
+{
+    private readonly IQuizRepository _quizRepository;
+    private readonly ILessonRepository _lessonRepository;
+
+    public CreateQuizCommandHandler(
+        IQuizRepository quizRepository,
+        ILessonRepository lessonRepository)
+    {
+        _quizRepository = quizRepository;
+        _lessonRepository = lessonRepository;
+    }
+
+    public async Task<QuizDto> Handle(CreateQuizCommand command, CancellationToken cancellationToken)
+    {
+        // Validate that the lesson exists
+        var lesson = await _lessonRepository.GetByIdAsync(command.QuizData.LessonId, cancellationToken);
+        if (lesson == null)
+            throw new NotFoundException("Lesson does not exist");
+
+        // Validate business rules
+        if (command.QuizData.PassingScore < 0 || command.QuizData.PassingScore > 100)
+        {
+            throw new ValidationException("Passing score must be between 0 and 100");
+        }
+
+        if (command.QuizData.TimeLimitMinutes < 0)
+        {
+            throw new ValidationException("Time limit cannot be negative");
+        }
+
+        // Convert DTO to domain entity
+        var quiz = command.QuizData.ToEntity();
+
+        // Add to repository
+        var createdQuiz = await _quizRepository.AddAsync(quiz, cancellationToken);
+
+        // Return DTO representation
+        return createdQuiz.ToDto();
+    }
+}
+
+/// <summary>
+/// Command for updating an existing quiz.
+/// </summary>
+public record UpdateQuizCommand(int Id, UpdateQuizDto QuizData) : ICommand<QuizDto?>;
+
+/// <summary>
+/// Handler for the UpdateQuizCommand.
+/// </summary>
+public class UpdateQuizCommandHandler : ICommandHandler<UpdateQuizCommand, QuizDto?>
+{
+    private readonly IQuizRepository _quizRepository;
+    private readonly ILessonRepository _lessonRepository;
+
+    public UpdateQuizCommandHandler(
+        IQuizRepository quizRepository,
+        ILessonRepository lessonRepository)
+    {
+        _quizRepository = quizRepository;
+        _lessonRepository = lessonRepository;
+    }
+
+    public async Task<QuizDto?> Handle(UpdateQuizCommand command, CancellationToken cancellationToken)
+    {
+        var quiz = await _quizRepository.GetByIdAsync(command.Id, cancellationToken);
+        if (quiz == null)
+            return null;
+
+        // Validate that the lesson exists
+        var lesson = await _lessonRepository.GetByIdAsync(command.QuizData.LessonId, cancellationToken);
+        if (lesson == null)
+            throw new NotFoundException("Lesson does not exist");
+
+        // Validate business rules
+        if (command.QuizData.PassingScore < 0 || command.QuizData.PassingScore > 100)
+        {
+            throw new ValidationException("Passing score must be between 0 and 100");
+        }
+
+        if (command.QuizData.TimeLimitMinutes < 0)
+        {
+            throw new ValidationException("Time limit cannot be negative");
+        }
+
+        // Update the quiz
+        quiz.UpdateFromDto(command.QuizData);
+        await _quizRepository.UpdateAsync(quiz, cancellationToken);
+
+        // Reload and return
+        var updatedQuiz = await _quizRepository.GetByIdAsync(command.Id, cancellationToken);
+        return updatedQuiz?.ToDto();
+    }
+}
+
+/// <summary>
+/// Command for deleting a quiz.
+/// </summary>
+public record DeleteQuizCommand(int Id) : ICommand<bool>;
+
+/// <summary>
+/// Handler for the DeleteQuizCommand.
+/// </summary>
+public class DeleteQuizCommandHandler : ICommandHandler<DeleteQuizCommand, bool>
+{
+    private readonly IQuizRepository _quizRepository;
+
+    public DeleteQuizCommandHandler(IQuizRepository quizRepository)
+    {
+        _quizRepository = quizRepository;
+    }
+
+    public async Task<bool> Handle(DeleteQuizCommand command, CancellationToken cancellationToken)
+    {
+        var quiz = await _quizRepository.GetByIdAsync(command.Id, cancellationToken);
+        if (quiz == null)
+            return false;
+
+        await _quizRepository.DeleteAsync(quiz, cancellationToken);
+        return true;
+    }
+}
+
+/// <summary>
+/// Command for getting a quiz with its questions.
+/// </summary>
+public record GetQuizWithQuestionsCommand(int Id) : ICommand<QuizWithQuestionsDto?>;
+
+/// <summary>
+/// Handler for the GetQuizWithQuestionsCommand.
+/// </summary>
+public class GetQuizWithQuestionsCommandHandler : ICommandHandler<GetQuizWithQuestionsCommand, QuizWithQuestionsDto?>
+{
+    private readonly IQuizRepository _quizRepository;
+
+    public GetQuizWithQuestionsCommandHandler(IQuizRepository quizRepository)
+    {
+        _quizRepository = quizRepository;
+    }
+
+    public async Task<QuizWithQuestionsDto?> Handle(GetQuizWithQuestionsCommand command, CancellationToken cancellationToken)
+    {
+        var quiz = await _quizRepository.GetWithQuestionsAsync(command.Id, cancellationToken);
+        return quiz?.ToQuizWithQuestionsDto();
+    }
+}

GermanApp/Domain/Entities/Quiz.cs

@@ -0,0 +1,182 @@
+namespace GermanApp.Domain.Entities;
+
+/// <summary>
+/// Represents a quiz that can be associated with a lesson.
+/// A quiz contains multiple questions and has a passing score threshold.
+/// </summary>
+public class Quiz
+{
+    public int Id { get; private set; }
+    public int LessonId { get; private set; }
+    public string Title { get; private set; } = string.Empty;
+    public string? Description { get; private set; }
+    public int PassingScore { get; private set; } = 80; // Default 80%
+    public int TimeLimitMinutes { get; private set; } = 0; // 0 = no limit
+    public bool IsActive { get; private set; } = true;
+    public bool ShuffleQuestions { get; private set; } = true;
+    public DateTime CreatedAt { get; private set; }
+    public DateTime? UpdatedAt { get; private set; }
+
+    // Navigation property
+    public virtual Lesson? Lesson { get; private set; }
+    public virtual ICollection<QuizQuestion> Questions { get; private set; } = new List<QuizQuestion>();
+
+    /// <summary>
+    /// Constructor for EF Core deserialization.
+    /// </summary>
+    private Quiz() { }
+
+    /// <summary>
+    /// Factory method to create a new quiz.
+    /// </summary>
+    /// <param name="lessonId">ID of the associated lesson</param>
+    /// <param name="title">Title of the quiz</param>
+    /// <param name="description">Optional description</param>
+    /// <param name="passingScore">Passing score percentage (default 80)</param>
+    /// <param name="timeLimitMinutes">Time limit in minutes (0 for no limit)</param>
+    public static Quiz Create(
+        int lessonId,
+        string title,
+        string? description = null,
+        int passingScore = 80,
+        int timeLimitMinutes = 0)
+    {
+        if (string.IsNullOrWhiteSpace(title))
+            throw new ArgumentException("Quiz title cannot be empty", nameof(title));
+        
+        if (passingScore < 0 || passingScore > 100)
+            throw new ArgumentOutOfRangeException(nameof(passingScore), "Passing score must be between 0 and 100");
+        
+        if (timeLimitMinutes < 0)
+            throw new ArgumentOutOfRangeException(nameof(timeLimitMinutes), "Time limit cannot be negative");
+
+        return new Quiz
+        {
+            LessonId = lessonId,
+            Title = title,
+            Description = description,
+            PassingScore = passingScore,
+            TimeLimitMinutes = timeLimitMinutes,
+            CreatedAt = DateTime.UtcNow
+        };
+    }
+
+    /// <summary>
+    /// Updates the quiz title.
+    /// </summary>
+    public void UpdateTitle(string newTitle)
+    {
+        if (string.IsNullOrWhiteSpace(newTitle))
+            throw new ArgumentException("Quiz title cannot be empty", nameof(newTitle));
+
+        Title = newTitle;
+        UpdatedAt = DateTime.UtcNow;
+    }
+
+    /// <summary>
+    /// Updates the quiz description.
+    /// </summary>
+    public void UpdateDescription(string? newDescription)
+    {
+        Description = newDescription;
+        UpdatedAt = DateTime.UtcNow;
+    }
+
+    /// <summary>
+    /// Updates the passing score.
+    /// </summary>
+    public void UpdatePassingScore(int newPassingScore)
+    {
+        if (newPassingScore < 0 || newPassingScore > 100)
+            throw new ArgumentOutOfRangeException(nameof(newPassingScore), "Passing score must be between 0 and 100");
+
+        PassingScore = newPassingScore;
+        UpdatedAt = DateTime.UtcNow;
+    }
+
+    /// <summary>
+    /// Updates the time limit.
+    /// </summary>
+    public void UpdateTimeLimit(int newTimeLimitMinutes)
+    {
+        if (newTimeLimitMinutes < 0)
+            throw new ArgumentOutOfRangeException(nameof(newTimeLimitMinutes), "Time limit cannot be negative");
+
+        TimeLimitMinutes = newTimeLimitMinutes;
+        UpdatedAt = DateTime.UtcNow;
+    }
+
+    /// <summary>
+    /// Updates the associated lesson.
+    /// </summary>
+    public void UpdateLesson(int newLessonId)
+    {
+        LessonId = newLessonId;
+        UpdatedAt = DateTime.UtcNow;
+    }
+
+    /// <summary>
+    /// Updates the shuffle questions setting.
+    /// </summary>
+    public void UpdateShuffleQuestions(bool newShuffleQuestions)
+    {
+        ShuffleQuestions = newShuffleQuestions;
+        UpdatedAt = DateTime.UtcNow;
+    }
+
+    /// <summary>
+    /// Activates the quiz.
+    /// </summary>
+    public void Activate()
+    {
+        IsActive = true;
+        UpdatedAt = DateTime.UtcNow;
+    }
+
+    /// <summary>
+    /// Deactivates the quiz.
+    /// </summary>
+    public void Deactivate()
+    {
+        IsActive = false;
+        UpdatedAt = DateTime.UtcNow;
+    }
+
+    /// <summary>
+    /// Adds a question to this quiz.
+    /// </summary>
+    public void AddQuestion(QuizQuestion question)
+    {
+        if (question == null)
+            throw new ArgumentNullException(nameof(question));
+        
+        Questions.Add(question);
+    }
+
+    /// <summary>
+    /// Removes a question from this quiz.
+    /// </summary>
+    public void RemoveQuestion(QuizQuestion question)
+    {
+        if (question == null)
+            throw new ArgumentNullException(nameof(question));
+        
+        Questions.Remove(question);
+    }
+
+    /// <summary>
+    /// Checks if the quiz is passed based on a score percentage.
+    /// </summary>
+    public bool IsPassed(double scorePercentage) => scorePercentage >= PassingScore;
+
+    /// <summary>
+    /// Calculates the score percentage based on correct answers.
+    /// </summary>
+    public double CalculateScore(int correctAnswers, int totalQuestions)
+    {
+        if (totalQuestions == 0)
+            return 0;
+        
+        return (double)correctAnswers / totalQuestions * 100;
+    }
+}

GermanApp/Domain/Entities/QuizQuestion.cs

@@ -1,17 +1,18 @@
 namespace GermanApp.Domain.Entities;
 
 /// <summary>
-/// Represents a quiz question for a lesson.
+/// Represents a quiz question for a quiz.
 /// Each question has a type (multiple choice, true/false, fill-in-the-blank, etc.)
-/// and is associated with a specific lesson.
+/// and is associated with a specific quiz.
 /// </summary>
 public class QuizQuestion
 {
     public int Id { get; private set; }
-    public int LessonId { get; private set; }
+    public int QuizId { get; private set; }
     public string QuestionText { get; private set; } = string.Empty;
     public QuestionType Type { get; private set; }
     public string? CorrectAnswer { get; private set; }
+    public int Points { get; private set; } = 1; // Points for this question
     public int Difficulty { get; private set; } // 1-5 scale
     public int Order { get; private set; }
     public bool IsActive { get; private set; } = true;
@@ -19,7 +20,7 @@ public class QuizQuestion
     public DateTime? UpdatedAt { get; private set; }
 
     // Navigation property
-    public virtual Lesson? Lesson { get; private set; }
+    public virtual Quiz? Quiz { get; private set; }
     public virtual ICollection<QuizOption> Options { get; private set; } = new List<QuizOption>();
 
     /// <summary>
@@ -30,32 +31,38 @@ public class QuizQuestion
     /// <summary>
     /// Factory method to create a new quiz question.
     /// </summary>
-    /// <param name="lessonId">ID of the parent lesson</param>
+    /// <param name="quizId">ID of the parent quiz</param>
     /// <param name="questionText">The question text</param>
     /// <param name="type">The question type</param>
     /// <param name="correctAnswer">The correct answer</param>
-    /// <param name="difficulty">Difficulty level (1-5)</param>
+    /// <param name="points">Points for this question (default 1)</param>
-    /// <param name="order">Sort order within the lesson</param>
+    /// <param name="difficulty">Difficulty level (1-5, default 3)</param>
+    /// <param name="order">Sort order within the quiz</param>
     public static QuizQuestion Create(
-        int lessonId,
+        int quizId,
         string questionText,
         QuestionType type,
         string correctAnswer,
+        int points = 1,
         int difficulty = 3,
         int order = 1)
     {
         if (difficulty < 1 || difficulty > 5)
             throw new ArgumentOutOfRangeException(nameof(difficulty), "Difficulty must be between 1 and 5");
         
+        if (points < 0)
+            throw new ArgumentOutOfRangeException(nameof(points), "Points must be positive");
+        
         if (string.IsNullOrWhiteSpace(questionText))
             throw new ArgumentException("Question text cannot be empty", nameof(questionText));
 
         return new QuizQuestion
         {
-            LessonId = lessonId,
+            QuizId = quizId,
             QuestionText = questionText,
             Type = type,
             CorrectAnswer = correctAnswer,
+            Points = points,
             Difficulty = difficulty,
             Order = order,
             CreatedAt = DateTime.UtcNow
@@ -83,6 +90,18 @@ public class QuizQuestion
         UpdatedAt = DateTime.UtcNow;
     }
 
+    /// <summary>
+    /// Updates the points for this question.
+    /// </summary>
+    public void UpdatePoints(int newPoints)
+    {
+        if (newPoints < 0)
+            throw new ArgumentOutOfRangeException(nameof(newPoints), "Points must be positive");
+
+        Points = newPoints;
+        UpdatedAt = DateTime.UtcNow;
+    }
+
     /// <summary>
     /// Updates the difficulty level.
     /// </summary>
@@ -114,11 +133,11 @@ public class QuizQuestion
     }
 
     /// <summary>
-    /// Updates the associated lesson.
+    /// Updates the associated quiz.
     /// </summary>
-    public void UpdateLesson(int newLessonId)
+    public void UpdateQuiz(int newQuizId)
     {
-        LessonId = newLessonId;
+        QuizId = newQuizId;
         UpdatedAt = DateTime.UtcNow;
     }
 

GermanApp/Domain/Interfaces/IRepository.cs

@@ -173,6 +173,76 @@ public interface IQuizQuestionRepository : IRepository<QuizQuestion, int>
     /// Checks if a quiz question with the given order exists in a lesson.
     /// </summary>
     Task<bool> OrderExistsInLessonAsync(int lessonId, int order, int? excludeId = null, CancellationToken cancellationToken = default);
+
+    // ============================================
+    // Quiz-based methods (QuizId)
+    // ============================================
+
+    /// <summary>
+    /// Gets quiz questions by quiz ID.
+    /// </summary>
+    Task<IReadOnlyList<QuizQuestion>> GetByQuizAsync(int quizId, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Gets active quiz questions by quiz ID.
+    /// </summary>
+    Task<IReadOnlyList<QuizQuestion>> GetActiveByQuizAsync(int quizId, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Gets quiz questions by quiz with options loaded.
+    /// </summary>
+    Task<IReadOnlyList<QuizQuestion>> GetByQuizWithOptionsAsync(int quizId, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Gets a random set of quiz questions for a quiz.
+    /// </summary>
+    Task<IReadOnlyList<QuizQuestion>> GetRandomQuestionsForQuizAsync(int quizId, int count, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Gets the total points for a quiz.
+    /// </summary>
+    Task<int> GetTotalPointsForQuizAsync(int quizId, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Checks if a quiz question with the given order exists in a quiz.
+    /// </summary>
+    Task<bool> OrderExistsInQuizAsync(int quizId, int order, int? excludeId = null, CancellationToken cancellationToken = default);
+}
+
+/// <summary>
+/// Repository interface for Quiz entities.
+/// </summary>
+public interface IQuizRepository : IRepository<Quiz, int>
+{
+    /// <summary>
+    /// Gets quizzes by lesson ID.
+    /// </summary>
+    Task<IReadOnlyList<Quiz>> GetByLessonAsync(int lessonId, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Gets all quizzes ordered by lesson and quiz order.
+    /// </summary>
+    Task<IReadOnlyList<Quiz>> GetAllOrderedAsync(CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Gets active quizzes by lesson ID.
+    /// </summary>
+    Task<IReadOnlyList<Quiz>> GetActiveByLessonAsync(int lessonId, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Gets a quiz with its questions and options.
+    /// </summary>
+    Task<Quiz?> GetWithQuestionsAsync(int id, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Gets the first quiz for a lesson.
+    /// </summary>
+    Task<Quiz?> GetFirstByLessonAsync(int lessonId, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Checks if a quiz exists for a lesson.
+    /// </summary>
+    Task<bool> ExistsByLessonAsync(int lessonId, CancellationToken cancellationToken = default);
 }
 
 /// <summary>

GermanApp/Infrastructure/Data/DbContext/AppDbContext.cs

@@ -19,6 +19,7 @@ public class AppDbContext : Microsoft.EntityFrameworkCore.DbContext
     public DbSet<User> Users { get; set; } = null!;
     public DbSet<UserProgress> UserProgress { get; set; } = null!;
     public DbSet<RefreshToken> RefreshTokens { get; set; } = null!;
+    public DbSet<Quiz> Quizzes { get; set; } = null!;
     public DbSet<QuizQuestion> QuizQuestions { get; set; } = null!;
     public DbSet<QuizOption> QuizOptions { get; set; } = null!;
 
@@ -134,17 +135,17 @@ public class AppDbContext : Microsoft.EntityFrameworkCore.DbContext
                    .OnDelete(DeleteBehavior.Cascade);
         });
 
-        // Configure QuizQuestion entity
+        // Configure Quiz entity
-        modelBuilder.Entity<QuizQuestion>(builder =>
+        modelBuilder.Entity<Quiz>(builder =>
         {
             builder.HasKey(q => q.Id);
             builder.Property(q => q.LessonId).IsRequired();
-            builder.Property(q => q.QuestionText).IsRequired().HasMaxLength(2000);
+            builder.Property(q => q.Title).IsRequired().HasMaxLength(200);
-            builder.Property(q => q.Type).IsRequired();
+            builder.Property(q => q.Description).HasMaxLength(2000);
-            builder.Property(q => q.CorrectAnswer).HasMaxLength(1000);
+            builder.Property(q => q.PassingScore).IsRequired().HasDefaultValue(80);
-            builder.Property(q => q.Difficulty).IsRequired().HasDefaultValue(3);
+            builder.Property(q => q.TimeLimitMinutes).HasDefaultValue(0);
-            builder.Property(q => q.Order).IsRequired().HasDefaultValue(1);
             builder.Property(q => q.IsActive).HasDefaultValue(true);
+            builder.Property(q => q.ShuffleQuestions).HasDefaultValue(true);
             builder.Property(q => q.CreatedAt).IsRequired();
             builder.Property(q => q.UpdatedAt).IsRequired(false);
 
@@ -154,8 +155,36 @@ public class AppDbContext : Microsoft.EntityFrameworkCore.DbContext
                    .HasForeignKey(q => q.LessonId)
                    .OnDelete(DeleteBehavior.Cascade);
 
-            // Unique constraint: one question per lesson per order
+            // Navigation to questions
-            builder.HasIndex(q => new { q.LessonId, q.Order }).IsUnique();
+            builder.HasMany(q => q.Questions)
+                   .WithOne(qq => qq.Quiz)
+                   .HasForeignKey(qq => qq.QuizId)
+                   .OnDelete(DeleteBehavior.Cascade);
+        });
+
+        // Configure QuizQuestion entity
+        modelBuilder.Entity<QuizQuestion>(builder =>
+        {
+            builder.HasKey(q => q.Id);
+            builder.Property(q => q.QuizId).IsRequired();
+            builder.Property(q => q.QuestionText).IsRequired().HasMaxLength(2000);
+            builder.Property(q => q.Type).IsRequired();
+            builder.Property(q => q.CorrectAnswer).HasMaxLength(1000);
+            builder.Property(q => q.Points).IsRequired().HasDefaultValue(1);
+            builder.Property(q => q.Difficulty).IsRequired().HasDefaultValue(3);
+            builder.Property(q => q.Order).IsRequired().HasDefaultValue(1);
+            builder.Property(q => q.IsActive).HasDefaultValue(true);
+            builder.Property(q => q.CreatedAt).IsRequired();
+            builder.Property(q => q.UpdatedAt).IsRequired(false);
+
+            // Foreign key to Quiz
+            builder.HasOne(q => q.Quiz)
+                   .WithMany(qq => qq.Questions)
+                   .HasForeignKey(q => q.QuizId)
+                   .OnDelete(DeleteBehavior.Cascade);
+
+            // Unique constraint: one question per quiz per order
+            builder.HasIndex(q => new { q.QuizId, q.Order }).IsUnique();
 
             // Navigation to options
             builder.HasMany(q => q.Options)

GermanApp/Infrastructure/Data/Repositories/QuizQuestionRepository.cs

@@ -21,7 +21,8 @@ public class QuizQuestionRepository : IQuizQuestionRepository
     public async Task<QuizQuestion?> GetByIdAsync(int id, CancellationToken cancellationToken = default)
     {
         return await _context.QuizQuestions
-            .Include(q => q.Lesson)
+            .Include(q => q.Quiz)
+            .ThenInclude(q => q.Lesson)
             .Include(q => q.Options.OrderBy(o => o.Order))
             .FirstOrDefaultAsync(q => q.Id == id, cancellationToken);
     }
@@ -29,7 +30,8 @@ public class QuizQuestionRepository : IQuizQuestionRepository
     public async Task<IReadOnlyList<QuizQuestion>> GetAllAsync(CancellationToken cancellationToken = default)
     {
         return await _context.QuizQuestions
-            .Include(q => q.Lesson)
+            .Include(q => q.Quiz)
+            .ThenInclude(q => q.Lesson)
             .Include(q => q.Options)
             .AsNoTracking()
             .ToListAsync(cancellationToken);
@@ -63,9 +65,10 @@ public class QuizQuestionRepository : IQuizQuestionRepository
     public async Task<IReadOnlyList<QuizQuestion>> GetByLessonAsync(int lessonId, CancellationToken cancellationToken = default)
     {
         return await _context.QuizQuestions
-            .Include(q => q.Lesson)
+            .Include(q => q.Quiz)
+            .ThenInclude(q => q.Lesson)
             .Include(q => q.Options.OrderBy(o => o.Order))
-            .Where(q => q.LessonId == lessonId)
+            .Where(q => q.Quiz != null && q.Quiz.LessonId == lessonId)
             .OrderBy(q => q.Order)
             .AsNoTracking()
             .ToListAsync(cancellationToken);
@@ -74,9 +77,11 @@ public class QuizQuestionRepository : IQuizQuestionRepository
     public async Task<IReadOnlyList<QuizQuestion>> GetAllOrderedAsync(CancellationToken cancellationToken = default)
     {
         return await _context.QuizQuestions
-            .Include(q => q.Lesson)
+            .Include(q => q.Quiz)
+            .ThenInclude(q => q.Lesson)
             .Include(q => q.Options.OrderBy(o => o.Order))
-            .OrderBy(q => q.Lesson.Order)
+            .OrderBy(q => q.Quiz.Lesson.Order)
+            .ThenBy(q => q.Quiz.Id)
             .ThenBy(q => q.Order)
             .AsNoTracking()
             .ToListAsync(cancellationToken);
@@ -85,9 +90,10 @@ public class QuizQuestionRepository : IQuizQuestionRepository
     public async Task<IReadOnlyList<QuizQuestion>> GetActiveByLessonAsync(int lessonId, CancellationToken cancellationToken = default)
     {
         return await _context.QuizQuestions
-            .Include(q => q.Lesson)
+            .Include(q => q.Quiz)
+            .ThenInclude(q => q.Lesson)
             .Include(q => q.Options.OrderBy(o => o.Order))
-            .Where(q => q.LessonId == lessonId && q.IsActive)
+            .Where(q => q.Quiz != null && q.Quiz.LessonId == lessonId && q.IsActive)
             .OrderBy(q => q.Order)
             .AsNoTracking()
             .ToListAsync(cancellationToken);
@@ -96,9 +102,10 @@ public class QuizQuestionRepository : IQuizQuestionRepository
     public async Task<IReadOnlyList<QuizQuestion>> GetRandomQuestionsForLessonAsync(int lessonId, int count, CancellationToken cancellationToken = default)
     {
         return await _context.QuizQuestions
-            .Include(q => q.Lesson)
+            .Include(q => q.Quiz)
+            .ThenInclude(q => q.Lesson)
             .Include(q => q.Options.OrderBy(o => o.Order))
-            .Where(q => q.LessonId == lessonId && q.IsActive)
+            .Where(q => q.Quiz != null && q.Quiz.LessonId == lessonId && q.IsActive)
             .OrderBy(q => Guid.NewGuid()) // Random ordering
             .Take(count)
             .AsNoTracking()
@@ -108,7 +115,7 @@ public class QuizQuestionRepository : IQuizQuestionRepository
     public async Task<IReadOnlyList<QuizQuestion>> GetByDifficultyAsync(int difficulty, CancellationToken cancellationToken = default)
     {
         return await _context.QuizQuestions
-            .Include(q => q.Lesson)
+            .Include(q => q.Quiz)
             .Include(q => q.Options)
             .Where(q => q.Difficulty == difficulty)
             .OrderBy(q => q.Order)
@@ -119,7 +126,7 @@ public class QuizQuestionRepository : IQuizQuestionRepository
     public async Task<IReadOnlyList<QuizQuestion>> GetByTypeAsync(QuestionType type, CancellationToken cancellationToken = default)
     {
         return await _context.QuizQuestions
-            .Include(q => q.Lesson)
+            .Include(q => q.Quiz)
             .Include(q => q.Options)
             .Where(q => q.Type == type)
             .OrderBy(q => q.Order)
@@ -130,7 +137,79 @@ public class QuizQuestionRepository : IQuizQuestionRepository
     public async Task<bool> OrderExistsInLessonAsync(int lessonId, int order, int? excludeId = null, CancellationToken cancellationToken = default)
     {
         var query = _context.QuizQuestions
-            .Where(q => q.LessonId == lessonId && q.Order == order);
+            .Where(q => q.Quiz != null && q.Quiz.LessonId == lessonId && q.Order == order);
+
+        if (excludeId.HasValue)
+        {
+            query = query.Where(q => q.Id != excludeId.Value);
+        }
+
+        return await query.AnyAsync(cancellationToken);
+    }
+
+    // ============================================
+    // Quiz-based methods (QuizId)
+    // ============================================
+
+    public async Task<IReadOnlyList<QuizQuestion>> GetByQuizAsync(int quizId, CancellationToken cancellationToken = default)
+    {
+        return await _context.QuizQuestions
+            .Include(q => q.Quiz)
+            .Include(q => q.Options.OrderBy(o => o.Order))
+            .Where(q => q.QuizId == quizId)
+            .OrderBy(q => q.Order)
+            .AsNoTracking()
+            .ToListAsync(cancellationToken);
+    }
+
+    public async Task<IReadOnlyList<QuizQuestion>> GetActiveByQuizAsync(int quizId, CancellationToken cancellationToken = default)
+    {
+        return await _context.QuizQuestions
+            .Include(q => q.Quiz)
+            .Include(q => q.Options.OrderBy(o => o.Order))
+            .Where(q => q.QuizId == quizId && q.IsActive)
+            .OrderBy(q => q.Order)
+            .AsNoTracking()
+            .ToListAsync(cancellationToken);
+    }
+
+    public async Task<IReadOnlyList<QuizQuestion>> GetByQuizWithOptionsAsync(int quizId, CancellationToken cancellationToken = default)
+    {
+        return await _context.QuizQuestions
+            .Include(q => q.Quiz)
+            .Include(q => q.Options.OrderBy(o => o.Order))
+            .Where(q => q.QuizId == quizId)
+            .OrderBy(q => q.Order)
+            .AsNoTracking()
+            .ToListAsync(cancellationToken);
+    }
+
+    public async Task<IReadOnlyList<QuizQuestion>> GetRandomQuestionsForQuizAsync(int quizId, int count, CancellationToken cancellationToken = default)
+    {
+        return await _context.QuizQuestions
+            .Include(q => q.Quiz)
+            .Include(q => q.Options.OrderBy(o => o.Order))
+            .Where(q => q.QuizId == quizId && q.IsActive)
+            .OrderBy(q => Guid.NewGuid()) // Random ordering
+            .Take(count)
+            .AsNoTracking()
+            .ToListAsync(cancellationToken);
+    }
+
+    public async Task<int> GetTotalPointsForQuizAsync(int quizId, CancellationToken cancellationToken = default)
+    {
+        var questions = await _context.QuizQuestions
+            .Where(q => q.QuizId == quizId && q.IsActive)
+            .Select(q => q.Points)
+            .ToListAsync(cancellationToken);
+        
+        return questions.Sum();
+    }
+
+    public async Task<bool> OrderExistsInQuizAsync(int quizId, int order, int? excludeId = null, CancellationToken cancellationToken = default)
+    {
+        var query = _context.QuizQuestions
+            .Where(q => q.QuizId == quizId && q.Order == order);
 
         if (excludeId.HasValue)
         {

GermanApp/Infrastructure/Data/Repositories/QuizRepository.cs

@@ -0,0 +1,114 @@
+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 IQuizRepository.
+/// This is part of the Infrastructure layer.
+/// </summary>
+public class QuizRepository : IQuizRepository
+{
+    private readonly AppDbContext _context;
+
+    public QuizRepository(AppDbContext context)
+    {
+        _context = context;
+    }
+
+    public async Task<Quiz?> GetByIdAsync(int id, CancellationToken cancellationToken = default)
+    {
+        return await _context.Quizzes
+            .Include(q => q.Lesson)
+            .FirstOrDefaultAsync(q => q.Id == id, cancellationToken);
+    }
+
+    public async Task<IReadOnlyList<Quiz>> GetAllAsync(CancellationToken cancellationToken = default)
+    {
+        return await _context.Quizzes
+            .Include(q => q.Lesson)
+            .AsNoTracking()
+            .ToListAsync(cancellationToken);
+    }
+
+    public async Task<Quiz> AddAsync(Quiz entity, CancellationToken cancellationToken = default)
+    {
+        await _context.Quizzes.AddAsync(entity, cancellationToken);
+        await _context.SaveChangesAsync(cancellationToken);
+        return entity;
+    }
+
+    public async Task UpdateAsync(Quiz entity, CancellationToken cancellationToken = default)
+    {
+        _context.Quizzes.Update(entity);
+        await _context.SaveChangesAsync(cancellationToken);
+    }
+
+    public async Task DeleteAsync(Quiz entity, CancellationToken cancellationToken = default)
+    {
+        _context.Quizzes.Remove(entity);
+        await _context.SaveChangesAsync(cancellationToken);
+    }
+
+    public async Task<bool> ExistsAsync(int id, CancellationToken cancellationToken = default)
+    {
+        return await _context.Quizzes
+            .AnyAsync(q => q.Id == id, cancellationToken);
+    }
+
+    public async Task<IReadOnlyList<Quiz>> GetByLessonAsync(int lessonId, CancellationToken cancellationToken = default)
+    {
+        return await _context.Quizzes
+            .Include(q => q.Lesson)
+            .Where(q => q.LessonId == lessonId)
+            .OrderBy(q => q.Id)
+            .AsNoTracking()
+            .ToListAsync(cancellationToken);
+    }
+
+    public async Task<IReadOnlyList<Quiz>> GetAllOrderedAsync(CancellationToken cancellationToken = default)
+    {
+        return await _context.Quizzes
+            .Include(q => q.Lesson)
+            .OrderBy(q => q.Lesson.Order)
+            .ThenBy(q => q.Id)
+            .AsNoTracking()
+            .ToListAsync(cancellationToken);
+    }
+
+    public async Task<IReadOnlyList<Quiz>> GetActiveByLessonAsync(int lessonId, CancellationToken cancellationToken = default)
+    {
+        return await _context.Quizzes
+            .Include(q => q.Lesson)
+            .Where(q => q.LessonId == lessonId && q.IsActive)
+            .OrderBy(q => q.Id)
+            .AsNoTracking()
+            .ToListAsync(cancellationToken);
+    }
+
+    public async Task<Quiz?> GetWithQuestionsAsync(int id, CancellationToken cancellationToken = default)
+    {
+        return await _context.Quizzes
+            .Include(q => q.Lesson)
+            .Include(q => q.Questions.OrderBy(qq => qq.Order))
+            .ThenInclude(qq => qq.Options.OrderBy(o => o.Order))
+            .FirstOrDefaultAsync(q => q.Id == id, cancellationToken);
+    }
+
+    public async Task<Quiz?> GetFirstByLessonAsync(int lessonId, CancellationToken cancellationToken = default)
+    {
+        return await _context.Quizzes
+            .Include(q => q.Lesson)
+            .Where(q => q.LessonId == lessonId && q.IsActive)
+            .OrderBy(q => q.Id)
+            .FirstOrDefaultAsync(cancellationToken);
+    }
+
+    public async Task<bool> ExistsByLessonAsync(int lessonId, CancellationToken cancellationToken = default)
+    {
+        return await _context.Quizzes
+            .AnyAsync(q => q.LessonId == lessonId, cancellationToken);
+    }
+}

GermanApp/Presentation/Controllers/QuizQuestionsController.cs

@@ -35,7 +35,20 @@ public class QuizQuestionsController : ControllerBase
     }
 
     /// <summary>
-    /// Gets all active quiz questions for a specific lesson.
+    /// Gets all active quiz questions for a specific quiz.
+    /// </summary>
+    /// <param name="quizId">The quiz ID</param>
+    /// <returns>List of quiz questions for the specified quiz</returns>
+    [HttpGet("by-quiz/{quizId}")]
+    [AllowAnonymous]
+    public async Task<IActionResult> GetQuizQuestionsByQuizAsync(int quizId, CancellationToken cancellationToken = default)
+    {
+        var questions = await _quizQuestionService.GetActiveQuizQuestionsByQuizAsync(quizId, cancellationToken);
+        return Ok(questions);
+    }
+
+    /// <summary>
+    /// Gets all active quiz questions for a specific lesson (legacy - uses first quiz).
     /// </summary>
     /// <param name="lessonId">The lesson ID</param>
     /// <returns>List of quiz questions for the specified lesson</returns>
@@ -63,12 +76,26 @@ public class QuizQuestionsController : ControllerBase
     }
 
     /// <summary>
-    /// Gets a random set of quiz questions for a lesson.
+    /// Gets a random set of quiz questions for a quiz.
+    /// </summary>
+    /// <param name="quizId">The quiz ID</param>
+    /// <param name="count">Number of questions to return</param>
+    /// <returns>List of random quiz questions for the quiz</returns>
+    [HttpGet("random/{quizId}/{count}")]
+    [AllowAnonymous]
+    public async Task<IActionResult> GetRandomQuizQuestionsForQuizAsync(int quizId, int count, CancellationToken cancellationToken = default)
+    {
+        var questions = await _quizQuestionService.GetRandomQuizQuestionsForQuizAsync(quizId, count, cancellationToken);
+        return Ok(questions);
+    }
+
+    /// <summary>
+    /// Gets a random set of quiz questions for a lesson (legacy - uses first quiz).
     /// </summary>
     /// <param name="lessonId">The lesson ID</param>
     /// <param name="count">Number of questions to return</param>
     /// <returns>List of random quiz questions for the lesson</returns>
-    [HttpGet("random/{lessonId}/{count}")]
+    [HttpGet("random/by-lesson/{lessonId}/{count}")]
     [AllowAnonymous]
     public async Task<IActionResult> GetRandomQuizQuestionsForLessonAsync(int lessonId, int count, CancellationToken cancellationToken = default)
     {
@@ -105,7 +132,7 @@ public class QuizQuestionsController : ControllerBase
     /// <summary>
     /// Creates a new quiz question.
     /// </summary>
-    /// <param name="dto">The quiz question data</param>
+    /// <param name="dto">The quiz question data (requires QuizId)</param>
     /// <returns>The created quiz question</returns>
     [HttpPost]
     [Authorize(Roles = "Admin")]
@@ -236,13 +263,15 @@ public class QuizQuestionsController : ControllerBase
     /// Submits quiz answers and returns the result.
     /// </summary>
     /// <param name="userId">The user ID</param>
-    /// <param name="dto">The quiz answers submission</param>
+    /// <param name="dto">The quiz answers submission (requires QuizId)</param>
     /// <returns>The quiz result</returns>
     [HttpPost("submit/{userId}")]
     [Authorize]
     public async Task<IActionResult> SubmitQuizAnswersAsync(int userId, SubmitQuizAnswersDto dto, CancellationToken cancellationToken = default)
     {
-        var result = await _quizQuestionService.SubmitQuizAnswersAsync(userId, dto, cancellationToken);
+        // Convert legacy DTO to new format
+        var newDto = new SubmitQuizDto(dto.QuizId, dto.Answers);
+        var result = await _quizQuestionService.SubmitQuizAnswersForQuizAsync(userId, newDto, cancellationToken);
         return Ok(result);
     }
 

GermanApp/Presentation/Controllers/QuizzesController.cs

@@ -0,0 +1,344 @@
+using GermanApp.Application.DTOs;
+using GermanApp.Application.Services;
+using GermanApp.Domain.Entities;
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+
+namespace GermanApp.Presentation.Controllers;
+
+/// <summary>
+/// API controller for managing quizzes.
+/// This is part of the Presentation layer.
+/// </summary>
+[ApiController]
+[Route("api/[controller]")]
+[Authorize]
+public class QuizzesController : ControllerBase
+{
+    private readonly QuizService _quizService;
+    private readonly QuizQuestionService _quizQuestionService;
+
+    public QuizzesController(
+        QuizService quizService,
+        QuizQuestionService quizQuestionService)
+    {
+        _quizService = quizService;
+        _quizQuestionService = quizQuestionService;
+    }
+
+    /// <summary>
+    /// Gets all quizzes.
+    /// </summary>
+    /// <returns>List of all quizzes</returns>
+    [HttpGet]
+    [AllowAnonymous]
+    public async Task<IActionResult> GetAllQuizzesAsync(CancellationToken cancellationToken = default)
+    {
+        var quizzes = await _quizService.GetAllQuizzesAsync(cancellationToken);
+        return Ok(quizzes);
+    }
+
+    /// <summary>
+    /// Gets all quizzes as list items (summary).
+    /// </summary>
+    /// <returns>List of quiz summary items</returns>
+    [HttpGet("list")]
+    [AllowAnonymous]
+    public async Task<IActionResult> GetAllQuizListItemsAsync(CancellationToken cancellationToken = default)
+    {
+        var quizzes = await _quizService.GetAllQuizListItemsAsync(cancellationToken);
+        return Ok(quizzes);
+    }
+
+    /// <summary>
+    /// Gets a specific quiz by its ID.
+    /// </summary>
+    /// <param name="id">The quiz ID</param>
+    /// <returns>The quiz with the specified ID</returns>
+    [HttpGet("{id}")]
+    [AllowAnonymous]
+    public async Task<IActionResult> GetQuizByIdAsync(int id, CancellationToken cancellationToken = default)
+    {
+        var quiz = await _quizService.GetQuizByIdAsync(id, cancellationToken);
+        if (quiz == null)
+            return NotFound();
+        return Ok(quiz);
+    }
+
+    /// <summary>
+    /// Gets a quiz with its questions by ID.
+    /// </summary>
+    /// <param name="id">The quiz ID</param>
+    /// <returns>The quiz with questions</returns>
+    [HttpGet("{id}/with-questions")]
+    [AllowAnonymous]
+    public async Task<IActionResult> GetQuizWithQuestionsAsync(int id, CancellationToken cancellationToken = default)
+    {
+        var quiz = await _quizService.GetQuizWithQuestionsAsync(id, cancellationToken);
+        if (quiz == null)
+            return NotFound();
+        return Ok(quiz);
+    }
+
+    /// <summary>
+    /// Gets all quizzes for a specific lesson.
+    /// </summary>
+    /// <param name="lessonId">The lesson ID</param>
+    /// <returns>List of quizzes for the specified lesson</returns>
+    [HttpGet("by-lesson/{lessonId}")]
+    [AllowAnonymous]
+    public async Task<IActionResult> GetQuizzesByLessonAsync(int lessonId, CancellationToken cancellationToken = default)
+    {
+        var quizzes = await _quizService.GetQuizzesByLessonAsync(lessonId, cancellationToken);
+        return Ok(quizzes);
+    }
+
+    /// <summary>
+    /// Gets active quizzes for a specific lesson.
+    /// </summary>
+    /// <param name="lessonId">The lesson ID</param>
+    /// <returns>List of active quizzes for the specified lesson</returns>
+    [HttpGet("active/by-lesson/{lessonId}")]
+    [AllowAnonymous]
+    public async Task<IActionResult> GetActiveQuizzesByLessonAsync(int lessonId, CancellationToken cancellationToken = default)
+    {
+        var quizzes = await _quizService.GetActiveQuizzesByLessonAsync(lessonId, cancellationToken);
+        return Ok(quizzes);
+    }
+
+    /// <summary>
+    /// Gets the first quiz for a lesson.
+    /// </summary>
+    /// <param name="lessonId">The lesson ID</param>
+    /// <returns>The first quiz for the lesson</returns>
+    [HttpGet("first/by-lesson/{lessonId}")]
+    [AllowAnonymous]
+    public async Task<IActionResult> GetFirstQuizByLessonAsync(int lessonId, CancellationToken cancellationToken = default)
+    {
+        var quiz = await _quizService.GetFirstQuizByLessonAsync(lessonId, cancellationToken);
+        if (quiz == null)
+            return NotFound();
+        return Ok(quiz);
+    }
+
+    /// <summary>
+    /// Gets all active quizzes.
+    /// </summary>
+    /// <returns>List of active quizzes</returns>
+    [HttpGet("active")]
+    [AllowAnonymous]
+    public async Task<IActionResult> GetActiveQuizzesAsync(CancellationToken cancellationToken = default)
+    {
+        var quizzes = await _quizService.GetActiveQuizzesAsync(cancellationToken);
+        return Ok(quizzes);
+    }
+
+    /// <summary>
+    /// Creates a new quiz.
+    /// </summary>
+    /// <param name="dto">The quiz data</param>
+    /// <returns>The created quiz</returns>
+    [HttpPost]
+    [Authorize(Roles = "Admin")]
+    public async Task<IActionResult> CreateQuizAsync(CreateQuizDto dto, CancellationToken cancellationToken = default)
+    {
+        var quiz = await _quizService.CreateQuizAsync(dto, cancellationToken);
+        return CreatedAtAction(nameof(GetQuizByIdAsync), new { id = quiz.Id }, quiz);
+    }
+
+    /// <summary>
+    /// Updates an existing quiz.
+    /// </summary>
+    /// <param name="id">The quiz ID</param>
+    /// <param name="dto">The updated quiz data</param>
+    /// <returns>The updated quiz</returns>
+    [HttpPut("{id}")]
+    [Authorize(Roles = "Admin")]
+    public async Task<IActionResult> UpdateQuizAsync(int id, UpdateQuizDto dto, CancellationToken cancellationToken = default)
+    {
+        var quiz = await _quizService.UpdateQuizAsync(id, dto, cancellationToken);
+        if (quiz == null)
+            return NotFound();
+        return Ok(quiz);
+    }
+
+    /// <summary>
+    /// Deletes a quiz by its ID.
+    /// </summary>
+    /// <param name="id">The quiz ID</param>
+    /// <returns>No content on success</returns>
+    [HttpDelete("{id}")]
+    [Authorize(Roles = "Admin")]
+    public async Task<IActionResult> DeleteQuizAsync(int id, CancellationToken cancellationToken = default)
+    {
+        var result = await _quizService.DeleteQuizAsync(id, cancellationToken);
+        if (!result)
+            return NotFound();
+        return NoContent();
+    }
+
+    /// <summary>
+    /// Activates a quiz.
+    /// </summary>
+    /// <param name="id">The quiz ID</param>
+    /// <returns>The activated quiz</returns>
+    [HttpPost("{id}/activate")]
+    [Authorize(Roles = "Admin")]
+    public async Task<IActionResult> ActivateQuizAsync(int id, CancellationToken cancellationToken = default)
+    {
+        var quiz = await _quizService.ActivateQuizAsync(id, cancellationToken);
+        if (quiz == null)
+            return NotFound();
+        return Ok(quiz);
+    }
+
+    /// <summary>
+    /// Deactivates a quiz.
+    /// </summary>
+    /// <param name="id">The quiz ID</param>
+    /// <returns>The deactivated quiz</returns>
+    [HttpPost("{id}/deactivate")]
+    [Authorize(Roles = "Admin")]
+    public async Task<IActionResult> DeactivateQuizAsync(int id, CancellationToken cancellationToken = default)
+    {
+        var quiz = await _quizService.DeactivateQuizAsync(id, cancellationToken);
+        if (quiz == null)
+            return NotFound();
+        return Ok(quiz);
+    }
+
+    /// <summary>
+    /// Checks if a quiz exists by ID.
+    /// </summary>
+    /// <param name="id">The quiz ID</param>
+    /// <returns>True if the quiz exists</returns>
+    [HttpGet("exists/{id}")]
+    [AllowAnonymous]
+    public async Task<IActionResult> ExistsAsync(int id, CancellationToken cancellationToken = default)
+    {
+        var exists = await _quizService.ExistsAsync(id, cancellationToken);
+        return Ok(new { exists });
+    }
+
+    /// <summary>
+    /// Checks if a quiz exists for a lesson.
+    /// </summary>
+    /// <param name="lessonId">The lesson ID</param>
+    /// <returns>True if a quiz exists for the lesson</returns>
+    [HttpGet("exists/by-lesson/{lessonId}")]
+    [AllowAnonymous]
+    public async Task<IActionResult> ExistsByLessonAsync(int lessonId, CancellationToken cancellationToken = default)
+    {
+        var exists = await _quizService.ExistsByLessonAsync(lessonId, cancellationToken);
+        return Ok(new { lessonId, exists });
+    }
+
+    /// <summary>
+    /// Gets the total number of quizzes.
+    /// </summary>
+    /// <returns>The total count of quizzes</returns>
+    [HttpGet("count")]
+    [AllowAnonymous]
+    public async Task<IActionResult> GetTotalQuizCountAsync(CancellationToken cancellationToken = default)
+    {
+        var count = await _quizService.GetTotalQuizCountAsync(cancellationToken);
+        return Ok(new { count });
+    }
+
+    /// <summary>
+    /// Gets the number of quizzes for a lesson.
+    /// </summary>
+    /// <param name="lessonId">The lesson ID</param>
+    /// <returns>The count of quizzes for the lesson</returns>
+    [HttpGet("count/by-lesson/{lessonId}")]
+    [AllowAnonymous]
+    public async Task<IActionResult> GetQuizCountByLessonAsync(int lessonId, CancellationToken cancellationToken = default)
+    {
+        var count = await _quizService.GetQuizCountByLessonAsync(lessonId, cancellationToken);
+        return Ok(new { lessonId, count });
+    }
+
+    /// <summary>
+    /// Gets quizzes by passing score range.
+    /// </summary>
+    /// <param name="minScore">Minimum passing score</param>
+    /// <param name="maxScore">Maximum passing score</param>
+    /// <returns>List of quizzes in the score range</returns>
+    [HttpGet("by-passing-score/{minScore}/{maxScore}")]
+    [AllowAnonymous]
+    public async Task<IActionResult> GetQuizzesByPassingScoreRangeAsync(int minScore, int maxScore, CancellationToken cancellationToken = default)
+    {
+        var quizzes = await _quizService.GetQuizzesByPassingScoreRangeAsync(minScore, maxScore, cancellationToken);
+        return Ok(quizzes);
+    }
+
+    /// <summary>
+    /// Gets quiz questions for a specific quiz.
+    /// </summary>
+    /// <param name="quizId">The quiz ID</param>
+    /// <returns>List of quiz questions for the quiz</returns>
+    [HttpGet("{quizId}/questions")]
+    [AllowAnonymous]
+    public async Task<IActionResult> GetQuizQuestionsByQuizAsync(int quizId, CancellationToken cancellationToken = default)
+    {
+        var questions = await _quizQuestionService.GetQuizQuestionsByQuizAsync(quizId, cancellationToken);
+        return Ok(questions);
+    }
+
+    /// <summary>
+    /// Gets active quiz questions for a specific quiz.
+    /// </summary>
+    /// <param name="quizId">The quiz ID</param>
+    /// <returns>List of active quiz questions for the quiz</returns>
+    [HttpGet("{quizId}/questions/active")]
+    [AllowAnonymous]
+    public async Task<IActionResult> GetActiveQuizQuestionsByQuizAsync(int quizId, CancellationToken cancellationToken = default)
+    {
+        var questions = await _quizQuestionService.GetActiveQuizQuestionsByQuizAsync(quizId, cancellationToken);
+        return Ok(questions);
+    }
+
+    /// <summary>
+    /// Gets random quiz questions for a quiz.
+    /// </summary>
+    /// <param name="quizId">The quiz ID</param>
+    /// <param name="count">Number of questions to return</param>
+    /// <returns>List of random quiz questions</returns>
+    [HttpGet("{quizId}/questions/random/{count}")]
+    [AllowAnonymous]
+    public async Task<IActionResult> GetRandomQuizQuestionsForQuizAsync(int quizId, int count, CancellationToken cancellationToken = default)
+    {
+        var questions = await _quizQuestionService.GetRandomQuizQuestionsForQuizAsync(quizId, count, cancellationToken);
+        return Ok(questions);
+    }
+
+    /// <summary>
+    /// Submits quiz answers and returns the result.
+    /// </summary>
+    /// <param name="userId">The user ID</param>
+    /// <param name="quizId">The quiz ID</param>
+    /// <param name="dto">The quiz answers submission</param>
+    /// <returns>The quiz result</returns>
+    [HttpPost("submit/{userId}/{quizId}")]
+    [Authorize]
+    public async Task<IActionResult> SubmitQuizAnswersAsync(int userId, int quizId, SubmitQuizDto dto, CancellationToken cancellationToken = default)
+    {
+        // Update the submission to use the correct quizId
+        var submission = new SubmitQuizDto(quizId, dto.Answers);
+        var result = await _quizQuestionService.SubmitQuizAnswersForQuizAsync(userId, submission, cancellationToken);
+        return Ok(result);
+    }
+
+    /// <summary>
+    /// Gets the total points for a quiz.
+    /// </summary>
+    /// <param name="quizId">The quiz ID</param>
+    /// <returns>The total points for the quiz</returns>
+    [HttpGet("{quizId}/total-points")]
+    [AllowAnonymous]
+    public async Task<IActionResult> GetTotalPointsForQuizAsync(int quizId, CancellationToken cancellationToken = default)
+    {
+        var points = await _quizQuestionService.GetTotalPointsForQuizAsync(quizId, cancellationToken);
+        return Ok(new { quizId, points });
+    }
+}

GermanApp/Program.cs

@@ -134,6 +134,7 @@ try
     builder.Services.AddScoped<ILevelRepository, LevelRepository>();
     builder.Services.AddScoped<ILessonRepository, LessonRepository>();
     builder.Services.AddScoped<IUserProgressRepository, UserProgressRepository>();
+    builder.Services.AddScoped<IQuizRepository, QuizRepository>();
     builder.Services.AddScoped<IQuizQuestionRepository, QuizQuestionRepository>();
     builder.Services.AddScoped<IQuizOptionRepository, QuizOptionRepository>();
 
@@ -171,9 +172,18 @@ try
     builder.Services.AddScoped<LevelService>();
     builder.Services.AddScoped<LessonService>();
     builder.Services.AddScoped<ProgressService>();
+    builder.Services.AddScoped<QuizService>();
     builder.Services.AddScoped<QuizQuestionService>();
     builder.Services.AddScoped<ICommandHandler<CreateLessonCommand, LessonDto>, CreateLessonCommandHandler>();
     
+    // Note: QuizQuestionService requires IQuizRepository which is registered above
+    
+    // Register Quiz command handlers
+    builder.Services.AddScoped<ICommandHandler<CreateQuizCommand, QuizDto>, CreateQuizCommandHandler>();
+    builder.Services.AddScoped<ICommandHandler<UpdateQuizCommand, QuizDto?>, UpdateQuizCommandHandler>();
+    builder.Services.AddScoped<ICommandHandler<DeleteQuizCommand, bool>, DeleteQuizCommandHandler>();
+    builder.Services.AddScoped<ICommandHandler<GetQuizWithQuestionsCommand, QuizWithQuestionsDto?>, GetQuizWithQuestionsCommandHandler>();
+
     var app = builder.Build();
 
     // Configure the HTTP request pipeline.