LoL sudden fps drops what to do?

Normally I never have problems with FPS, mostly they are 144. Since yesterday, however, I suddenly have the problem that my Fps drop significantly. It looks like I start a game, everything runs normally for 2 minutes and then the fps drop completely, sometimes to 21. And the laptop just crashes every 2-3 games, which never happened to me before. Can someone help me? What can that be?

Maybe something installed in time?

Also have such a problem. Could be due to an update or you had too many things in the background… Try lowering the graphics and if that doesn't work, 'fix' your game.