Thanks for your helpful suggestions.
I just went online again and avast updated automatically saying now it has 0515-3 and before had 0515-1 (remember: about dialogue and antivirus-program gui said always 0515-0 being installed and would not update).
Now all components say: 0515-3 installed, so everything fine and repaired “automatically”?! Can I forget the recent problems??? :
I think so, you can just monitor the situation and see if they come back.