Android app for images/videos viewer

- The app show only one photo with possible for next and previous.
- Sidebar show folders menu. Every folder contain photos or/and other folders
- Photos names can be also showed in the sidebar under their folder

- It exist two roles (admin, normal)
- Admin user is only one and already in database
- Other users are always normal
- Normal user must pay to show the viewer (paypal, mastercard, normal transfer, ...)
- Every normal user can login only in one mobile
- On try to login in other mobile deactivate the old login
- Every user can change his data

- Normal user can only read (show/navigate folders and photos)
- Admin can add/edit/delete/sort folders and photos
- Multi add photos is possible
- User (admin or normal) can add photos to favorite

- I need also to have and edit source code
- better with angular2 (when you need separate backend then better java)
- I need files to add more languages