I had an error while trying to add a beatmap and got the same error 3 times. After that, it said that I had no beatmaps, while I had a lot. Then I updated through the game, and that caused an error. Then I updated with the updater from the website, now it doesn't even start.
Tried the 2 installers and the updater, tried the file given here, ran in administrator mode and compatibility mode. Also restarted windows.
Also tried unninstaling, but it gives me the same error (osu! stopped working). Everything I do gives me that.
Here's the error that started everything.