diff --git a/apps/course/serializers/course.py b/apps/course/serializers/course.py
index 5f80645..312a788 100644
--- a/apps/course/serializers/course.py
+++ b/apps/course/serializers/course.py
@@ -2,7 +2,7 @@ from rest_framework import serializers
 
 # from dj_filer.admin import get_thumbs
 from utils import get_thumbs
-from apps.course.models import Course, CourseCategory, Attachment, Glossary, LessonCompletion, Participant, Lesson, CourseAttachment, CourseGlossary
+from apps.course.models import Course, CourseCategory, Attachment, Glossary, LessonCompletion, Participant, Lesson, CourseAttachment, CourseGlossary, CourseLesson
 from apps.chat.models import RoomMessage
 from apps.account.serializers import UserProfileSerializer
 
@@ -132,18 +132,18 @@ class CourseDetailSerializer(serializers.ModelSerializer):
             # آخرین درس تکمیل‌شده توسط کاربر
             last_completed_lesson = LessonCompletion.objects.filter(
                 student=user,
-                lesson__course=obj
+                course_lesson__course=obj
             ).order_by('-completed_at').first()
             
             if last_completed_lesson:
                 # پیدا کردن درس بعدی بر اساس priority
-                next_lesson = Lesson.objects.filter(
+                next_lesson = CourseLesson.objects.filter(
                     course=obj,
-                    priority__gt=last_completed_lesson.lesson.priority,
+                    priority__gt=last_completed_lesson.course_lesson.priority,
                     is_active=True
                 ).order_by('priority').first()
                 if not next_lesson:
-                    next_lesson = Lesson.objects.filter(
+                    next_lesson = CourseLesson.objects.filter(
                         course=obj,
                         is_active=True
                     ).order_by('priority').first()
@@ -190,7 +190,7 @@ class CourseDetailSerializer(serializers.ModelSerializer):
         """Helper method to count completed lessons for the student in the given course."""
         return LessonCompletion.objects.filter(
             student=student,
-            lesson__course=course
+            course_lesson__course=course
         ).count()
         
 
@@ -244,7 +244,7 @@ class MyCourseListSerializer(serializers.ModelSerializer):
         """Helper method to count completed lessons for the student in the given course."""
         return LessonCompletion.objects.filter(
             student=student,
-            lesson__course=course
+            course_lesson__course=course
         ).count()