If I try to save changes on styles (e.g. change font in standard style), the complete applicaion crashes. Restarting shows me the document recovery, but nothing changes. The old font is standard again.
Could you try this: https://wiki.documentfoundation.org/UserProfile#Resolving_corruption_in_the_user_profile If it doesn't help, you can try debugging (after installing debug package): https://wiki.documentfoundation.org/QA/BugReport/Debug_Information Set to NEEDINFO. Change back to UNCONFIRMED, if the problem persists after renaming user profile temporarily. Change to RESOLVED WORKSFORME, if the problem went away with a new profile.
I think this can be closed. Libre Office 4 and 5 were installed in parallel. I uninstalled both, cleaned my profile and installed Version 5 again. It works now without any problems. Thanks.
Ah, ok, let's set to WFM. Btw. if you want to help us test bugs it would be great: https://wiki.documentfoundation.org/QA/Triage_For_Beginners