Android app auto-download (offline use) + media player

Hey guys, I am fairly new to Nextcloud and I struggle a little with its Android App.

1 - Is there any way that all files/folders can be automatically downloaded to my phone file system for offline use? I don’t wanna download them one by one but even when I do and I wanna delete them later they don’t automatically sync (delete) from my ‘original’ nextcloud folder.

2 - If not, can I, anyhow, use my ‘native’ audio/video player, let’s say VLC, for playing media files instead of Nextcloud built-in player. I am really having hard times using that one.

The best solution for me is that all files download to my phone automatically whenever there’s a connection so I can use them anytime offline. And they sync once I am connected again.
Cheers.