public async void SaveQuiz()
        {
            QuizToEdit.Quistions = QuistionCollection.ToList();
            await PersistencyFacade.SaveQuizzesAsJsonAsync(QuizManager.Instance.Quizzes);

            MainViewModel.Instance.NavigateBack();
        }
        //Actions

        public void AddQuistion()
        {
            QuistionCollection.Add(_editedQuistion);
            _editedQuistion = new Quistion();
            SelectedIndex   = QuistionCollection.Count - 1;
            OnPropertyChanged(nameof(QuistionCollection));
        }
 public void DeleteQuistion()
 {
     QuistionCollection.RemoveAt(SelectedIndex);
     OnPropertyChanged(nameof(QuistionCollection));
 }