Removing the .Tribler map by APPDATA is successful, now it was possible to make a fresh installation. I have cleanup the system with CCleaner.
Unfortunately i have the same problems, i can't add Torrent files or magnetlinks.
After several times, starting up Tribler has been crashed again. Now i have installed an old version of Tribler 6.5.2 that work stable.
I hope quickly for an good stable working version for windows, that this problems be fix.