Thank you for your suggestions, @Wolfgang_S and @rlkoshak.
I reset the ownership but so far nothing changed. And I’ve been waiting for about an hour since I cleaned the cache. But Openhab does not seem to download anything. I checked the directories and it looks like all relevant files have been restored. My things, items and rules have been placed in their folders. As for /var/lib/openhab2 I cannot really tell a difference to check whether this is my configuration.