back button issue with push notification

Hi, my project is in Mvvm architecture. i am facing back button issue with push notification.( please help me thank in Advance )
project flow,
Homepage->Latestnewspage->LatestnewsDetailpage.
problem,

                              (refreshing here)

LatestnewsDetailpage<-Homepage<-Latestnewspage<-LatestnewsDetailpage.

here is my method

    public async Task LoadNotificationData()
    {
        if (Session.Instance.SelectedNews != null)--->when i am passing that SelectedNews==null back button problem is solved
                                                                                             But, pus notification not going to  LatestNewsDetailViewModel page it is going to Homepage
        {
            Navigation.Push(ViewFactory.CreatePage<LatestNewsDetailViewModel>());
        }
        else if (Session.Instance.SelectedECircular != null)
        {
            Navigation.Push(ViewFactory.CreatePage<ECirularsDetailViewModel>());
        }
        else if (Session.Instance.SelectedHomeWork != null)
        {
            Navigation.Push(ViewFactory.CreatePage<HomeWorkViewModel>());
        }
        else if (Session.Instance.SelectedAttendance != null)
        {
            Navigation.Push(ViewFactory.CreatePage<AttendanceViewModel>());
        }
        else if (Session.Instance.SelectedPhoto != null)
        {
            Navigation.Push(ViewFactory.CreatePage<PhotoGalleryViewModel>());
        }
        else if (Session.Instance.SelectedEvent != null)
        {
            Navigation.Push(ViewFactory.CreatePage<EventsAndCalendarViewModel>());
        }
        else if (Session.Instance.SelectedVideo != null)
        {
            Navigation.Push(ViewFactory.CreatePage<VideoGalleryViewModel>());
        }
        else if (Session.Instance.SelectedFeedback != null)
        {
            Session.Instance.FeedbackList = Session.Instance.SelectedFeedback;
            Navigation.Push(ViewFactory.CreatePage<SubjectWiseFeedbackViewModel>());
        }

        //if (MenuList == null || MenuList.Count == 0)
        await LoadMenuData();
        await LoadInstituteAndUserData();

        Task.Run(() =>
        {
            CheckFcmAndRegister();
        });

        //StringExtensions.sendEmail("FCM Token", Session.Instance.DeviceFCMToken);
    }