1. Just right click on the avast tray icon and select about avast. Or from the avastUI > Settings > About Avast.
2. having said "i dont want firefox-addons by avast. Thanks a lot" my assumption that you wanted them removed.
Though having disabled them, they are still there, removing them completely I would have thought would be better.
3. I believe the Details on the Smart Scan is an acknowledged bug (to be fixed). Having run the smart scan, go back AvastUI > Protection > Antivirus > Scan History, that should give you some information on the scan. Though it won't be much if there were no alerts you're only going to get duration and files scanned, etc.