diff --git a/backend/src/main/java/core/entities/timemanager/TaskSerie.java b/backend/src/main/java/core/entities/timemanager/TaskSerie.java
index bc12ba1..50be1c7 100644
--- a/backend/src/main/java/core/entities/timemanager/TaskSerie.java
+++ b/backend/src/main/java/core/entities/timemanager/TaskSerie.java
@@ -12,7 +12,7 @@ public class TaskSerie {
     @GeneratedValue(strategy = GenerationType.AUTO)
     private long taskSerieID;
 
-    @OneToMany(fetch = FetchType.EAGER, mappedBy = "taskSerie")
+    @OneToMany(fetch = FetchType.EAGER, mappedBy = "taskSerie", orphanRemoval = true)
     List<TaskSerieItem> tasks = new ArrayList<>();
 
 
diff --git a/backend/src/main/java/core/repositories/timemanager/TaskRepository.java b/backend/src/main/java/core/repositories/timemanager/TaskRepository.java
index d4f7268..208dbe6 100644
--- a/backend/src/main/java/core/repositories/timemanager/TaskRepository.java
+++ b/backend/src/main/java/core/repositories/timemanager/TaskRepository.java
@@ -20,6 +20,7 @@ public interface TaskRepository extends CrudRepository<Task, Long> {
 
     @Modifying
     @Transactional
+    @Query(value = "DELETE FROM Task t WHERE t.taskgroup = ?1")
     void deleteAllByTaskgroup(Taskgroup taskgroup);
 
     @Transactional
diff --git a/backend/src/main/java/core/repositories/timemanager/TaskSerieItemRepository.java b/backend/src/main/java/core/repositories/timemanager/TaskSerieItemRepository.java
index 0397bc7..73e9008 100644
--- a/backend/src/main/java/core/repositories/timemanager/TaskSerieItemRepository.java
+++ b/backend/src/main/java/core/repositories/timemanager/TaskSerieItemRepository.java
@@ -1,9 +1,19 @@
 package core.repositories.timemanager;
 
 import core.entities.timemanager.TaskSerieItem;
+import core.entities.timemanager.Taskgroup;
+import org.springframework.data.jpa.repository.Modifying;
+import org.springframework.data.jpa.repository.Query;
 import org.springframework.data.repository.CrudRepository;
 import org.springframework.stereotype.Repository;
 
+import javax.transaction.Transactional;
+
 @Repository
 public interface TaskSerieItemRepository extends CrudRepository<TaskSerieItem, Long> {
+
+    @Query(value = "DELETE FROM TaskSerieItem tsi WHERE tsi.task IN (SELECT t FROM Task t WHERE t.taskgroup = ?1)")
+    @Modifying
+    @Transactional
+    void deleteByTaskgroup(Taskgroup taskgroup);
 }
diff --git a/backend/src/main/java/core/repositories/timemanager/TaskSeriesRepository.java b/backend/src/main/java/core/repositories/timemanager/TaskSeriesRepository.java
index d03fc42..c0b7301 100644
--- a/backend/src/main/java/core/repositories/timemanager/TaskSeriesRepository.java
+++ b/backend/src/main/java/core/repositories/timemanager/TaskSeriesRepository.java
@@ -1,9 +1,23 @@
 package core.repositories.timemanager;
 
 import core.entities.timemanager.TaskSerie;
+import core.entities.timemanager.Taskgroup;
+import org.springframework.data.jpa.repository.Modifying;
+import org.springframework.data.jpa.repository.Query;
 import org.springframework.data.repository.CrudRepository;
+import org.springframework.data.repository.query.Param;
 import org.springframework.stereotype.Repository;
 
+import javax.transaction.Transactional;
+import java.util.List;
+
 @Repository
 public interface TaskSeriesRepository extends CrudRepository<TaskSerie, Long> {
+    @Query("SELECT DISTINCT ts FROM TaskSerie ts JOIN ts.tasks tsi JOIN tsi.task t WHERE t.taskgroup = :taskgroup")
+    List<TaskSerie> findByTaskgroup(@Param("taskgroup")Taskgroup taskgroup);
+
+    @Modifying
+    @Transactional
+    @Query(value = "DELETE FROM TaskSerie ts WHERE ts.tasks.size = 0")
+    void deleteUnreferenced();
 }
diff --git a/backend/src/main/java/core/services/TaskSeriesService.java b/backend/src/main/java/core/services/TaskSeriesService.java
index 65fa3b1..8c5614b 100644
--- a/backend/src/main/java/core/services/TaskSeriesService.java
+++ b/backend/src/main/java/core/services/TaskSeriesService.java
@@ -6,6 +6,7 @@ import core.api.models.timemanager.tasks.repeatinginfo.TaskRepeatWeekInfo;
 import core.entities.timemanager.Task;
 import core.entities.timemanager.TaskSerie;
 import core.entities.timemanager.TaskSerieItem;
+import core.entities.timemanager.Taskgroup;
 import core.repositories.timemanager.TaskRepository;
 import core.repositories.timemanager.TaskSerieItemRepository;
 import core.repositories.timemanager.TaskSeriesRepository;
@@ -40,7 +41,6 @@ public class TaskSeriesService {
         rootTask.setTaskSerieItem(rootItem);
 
         LocalDate currentTaskDate = rootTask.getStartDate().plusDays(taskRepeatInfo.getOffset());
-        int index = 2;
         while(currentTaskDate.isBefore(taskRepeatInfo.getEndingDate())) {
             Task task = Task.cloneTask(rootTask);
             task.setStartDate(currentTaskDate);
@@ -53,7 +53,6 @@ public class TaskSeriesService {
             taskList.add(task);
             task.setTaskSerieItem(taskSerieItem);
             currentTaskDate = currentTaskDate.plusDays(taskRepeatInfo.getOffset());
-            index++;
         }
 
         taskSeriesRepository.save(taskSerie);
@@ -77,6 +76,11 @@ public class TaskSeriesService {
         }
     }
 
+    public void deleteTaskSerieByTaskgroup(Taskgroup taskgroup) {
+        taskSerieItemRepository.deleteByTaskgroup(taskgroup);
+        taskSeriesRepository.deleteUnreferenced();
+    }
+
     public static String convertIndexToString(int index) {
         if(index < 10) {
             return "0" + index;
diff --git a/backend/src/main/java/core/services/TaskService.java b/backend/src/main/java/core/services/TaskService.java
index 8677e1d..d3b4e4a 100644
--- a/backend/src/main/java/core/services/TaskService.java
+++ b/backend/src/main/java/core/services/TaskService.java
@@ -100,6 +100,7 @@ public class TaskService {
     }
 
     public void clearTasks(Taskgroup taskgroup) {
+        taskSeriesService.deleteTaskSerieByTaskgroup(taskgroup);
         taskRepository.deleteAllByTaskgroup(taskgroup);
     }