How to use Android App for syncing files.

Hi everyone, I’ve been searching through these topics and I’m struggling with two questions about the Android app for nextcloud. My android nextcloud app is connected to my nextcloud server. On my Android client I pressed the + button and then upload files. Then I selected a folder on my android device with pictures in it. It uploaded those photos to my Nextcloud server.

Question 1: If I delete files on Nextcloud, either through web app or android app, the files on my android phone are not deleted. Google photos actually deletes them from my phone if I delete them in Google photos. I’m kinda guessing from the posts that this a limitation of Nextcloud, or am I doing something wrong?

Question 2: How is Android → Settings → Auto upload different from uploading a folder using the + button? When I tried Auto upload → press cloud button, nothing happened.

Does anyone know of documentation anywhere that would explain these two things?

Thanks in advance.