I want to add list elements but fragment doesnt update in adapter

I wanna try a bookmark system for my app and I already have a working listview displaying all the events. now I wanna give the user the opportunity to bookmark them. After bookmarking, they should be displayed in a new fragment but it is not working. You can bookmark successfully but the list is just saving one element and that's it. Furthermore, the one additionally added item will not be displayed in the bookmarking fragment. I tried to integrate notifyDataSetChanged() successfully but I cannot integrate the Favorite Base Adapter to use this function.

This is some code from my Custom Adapter, which is showing all events a user can attend a seperate listView

public class CustomArrayAdapter extends BaseAdapter{

private List<EventItem> listData;

List<EventItem> fList = new ArrayList<EventItem>();

private LayoutInflater layoutInflater;

private Context context;

static class ViewHolder {
    TextView titleView;
    TextView descriptionView;
    TextView authorView;
    TextView reportedDateView;
    TextView locationView;
    ImageView favorite;
}

public CustomArrayAdapter(Context context, List<EventItem> listData) {
    this.context = context;
    this.listData = listData;
    Collections.sort(listData);
}

@Override
public int getCount() {
    return listData.size();
}

@Override
public Object getItem(int position) {
    return listData.get(position);
}

@Override
public long getItemId(int position) {
    return position;
}

public View getView(final int position, View convertView, ViewGroup parent) {
    final ViewHolder holder;
    if (convertView == null) {
        layoutInflater = (LayoutInflater) this.context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = layoutInflater.inflate(R.layout.list_event_item, null);
        holder = new ViewHolder();

        holder.titleView = (TextView) convertView.findViewById(R.id.title);
        holder.authorView = (TextView) convertView.findViewById(R.id.author);
        holder.descriptionView = (TextView) convertView.findViewById(R.id.description);
        holder.locationView = (TextView) convertView.findViewById(R.id.location);
        holder.reportedDateView = (TextView) convertView.findViewById(R.id.time);

        convertView.setTag(holder);

    } else {
        holder = (ViewHolder) convertView.getTag();
    }
        holder.titleView.setText(listData.get(position).getTitle());
        holder.authorView.setText(listData.get(position).getAuthor());
        holder.descriptionView.setText(listData.get(position).getDescription());
        holder.locationView.setText(listData.get(position).getLocation());
        holder.reportedDateView.setText(getTime(position));

    /*ermöglicht bookmark*/
    holder.favorite = (ImageView) convertView.findViewById(R.id.bookmark);

    holder.favorite.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            listData.get(position).isSelected=!listData.get(position).isSelected;
            notifyDataSetChanged();

            if(listData.get(position).isSelected){
                //addingFlist(listData.get(position), fList);
                //System.out.println(listData.get(position));


                **here should be the bookmark function to add it**

                //Favorites.getInstance().adding(listData.get(position));
                notifyDataSetChanged();
            }
        }
    });

    if(listData.get(position).isSelected){
        holder.favorite.setSelected(true);
    }else{
        holder.favorite.setSelected(false);
    }
 /**/

    return convertView;
}

Here my favorite class, where I wanted to save all the functions like adding, deleting etc

public class Favorites {

private List<EventItem> markierteListe = new ArrayList<EventItem>();;

public static Favorites getInstance(){
    return new Favorites();
}

public List<EventItem> getMarkierteListe() { return this.markierteListe; }

   private Favorites() {
   this.fillList();
}

private void fillList() {
    this.markierteListe.add(new EventItem("Titel 2", "Autor 2", "Ort 2 ", "Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat", new Date(System.currentTimeMillis()), new Date(System.currentTimeMillis())));
    this.markierteListe.add(new EventItem("Titel 3", "Autor 3", "Ort 3 ", "Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat", new Date(System.currentTimeMillis()), new Date(System.currentTimeMillis())));
    this.markierteListe.add(new EventItem("Titel 6", "Autor 6", "Ort 6 ", "Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat", new Date(System.currentTimeMillis()), new Date(System.currentTimeMillis())));
    this.markierteListe.add(new EventItem("Titel 8", "Autor 8", "Ort 8 ", "Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat", new Date(System.currentTimeMillis()), new Date(System.currentTimeMillis())));
    this.markierteListe.add(new EventItem("Titel 13", "Autor 13", "Ort 13 ", "Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat", new Date(System.currentTimeMillis()), new Date(System.currentTimeMillis())));
}

public void adding(EventItem eventItem){
    //fList.add(eventItem);
    System.out.println("###");
    this.markierteListe.add(eventItem);

    for (int i = 0; i < this.markierteListe.size(); i++) {
        System.out.println("Index: " + i + " - Item: " + this.markierteListe.get(i));
    }
}

}

Here the adapter to display the favorite ones in a listview

public class FavoriteArrayAdapter extends BaseAdapter {

private List<EventItem> boomarkedData;
private LayoutInflater layoutInflater;
private Context context;

static class ViewHolder {
    TextView titel;
    TextView autor;
    TextView ort;
    ImageView delete;
}

public FavoriteArrayAdapter(Context context, List<EventItem> boomarkedData) {
    this.context = context;
    this.boomarkedData = boomarkedData;
    Collections.sort(boomarkedData);
}

@Override
public int getCount() {
    return boomarkedData.size();
}

@Override
public Object getItem(int position) {
    return boomarkedData.get(position);
}

@Override
public long getItemId(int position) {
    return position;
}

public View getView(final int position, View convertView, ViewGroup parent) {
    final FavoriteArrayAdapter.ViewHolder holder;
    if (convertView == null) {
        layoutInflater = (LayoutInflater) this.context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = layoutInflater.inflate(R.layout.favorite_event_item, null);
        holder = new FavoriteArrayAdapter.ViewHolder();

        holder.titel = (TextView) convertView.findViewById(R.id.titel);
        holder.autor = (TextView) convertView.findViewById(R.id.autor);
        holder.ort = (TextView) convertView.findViewById(R.id.ort);

        convertView.setTag(holder);

    } else {
        holder = (FavoriteArrayAdapter.ViewHolder) convertView.getTag();
    }

    holder.titel.setText(boomarkedData.get(position).getTitle());
    holder.autor.setText(boomarkedData.get(position).getAuthor());
    holder.ort.setText(boomarkedData.get(position).getLocation());

    /*ermöglicht löschen*/
    holder.delete = (ImageView) convertView.findViewById(R.id.delete);

    return convertView;
}

Here the fragment for the favorite ones

public class WorkInProgressFragment extends Fragment {

private View view;
private TextView textView;
private ListView favoritenListe;

private TextView titel;
private TextView autor;
private TextView ort;


@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
    view = inflater.inflate(R.layout.work_in_progress_layout, container, false);

    favoritenListe = view.findViewById(R.id.favoritenListe);
    final FavoriteArrayAdapter favoriteArrayAdapter = new FavoriteArrayAdapter(getContext(), Favorites.getInstance().getMarkierteListe());
    favoritenListe.setAdapter(favoriteArrayAdapter);

    return view;
}