please help me with my fps problems

ok so my computer got repaired 1 week ago, and when i downloaded league of legends everything was incredibly smooth and i was playing on 200fps+. And i was playing like this for many days, but then there was an update or downtime today (05.06.2019) and when i tried to play for some weird reason when i dont move my fps is just stuck at 40, and when i move it goes up and down from 20-70 fps super fast. and i have tried everything in the settings you can think of. If someone has had the same problem or know how to fix it please help me.