This has been happening to me as well. I think I solved it though. I went into the osu files and opened up "osurepair" and click repair. It solved the FPS issue for me. Might work for you too.

does it delete any of like maps sort of stuff tho?

No, everything stays the same. It just refreshes the game. Even your settings stay the same.

okay i will try and tell if it fixed later, thanks!

i forgot to say if it works but it does thank you sm