Nextcloud sync - disappearing files

[Baryonics]

Hello all,
I just downloaded saber and ran into some weird issues. First things first: I'm no developer, nor do I have any experience with nextcloud.
What I did:

1. Installed saber on 3 devices (Android Tablet and Phone, Windows Notebook)
2. Registered with the "sign up now!" dialog
3. Logged in on every device using the "Verficication code" from the verification E-Mail as "Encryption password" (which seems odd, but somehow the login works)
4. Created files on every device for testing

Problem is: if I create a file on my phone, sync, then edit it on my tablet, it will disapear on both devices. It won't show up on my notebook at any time.

When clicking "Server homepage" on my Notebook, it will just open the directory of sable in Explorer.
On both android devices, this leads me to the Saber dashboard, in whick I can see some cryptip .sbe and .sbc files.

Be kind, I'm a confused user that stranded on GitHub because of the lack of a forum, not a developer...
Enjoying the App so far (except losing my lecture notes from today)