[2019] Fps problems on my laptop

So after I just install the game, I get constant 144fps on my Lenovo legion laptop. But after a few days it starts to go down. And it comes to a point to 60-80 fps during fights and it becomes hard to aim. If I reinstall the game, it goes back up to 144 fps. And it's smooth as butter on 1080p. But after a few days I get 70-80 fps even on 900p. How do I fix this? I tried deleting the GameUserSettings.ini. It didn't work. It's become hard to play the game now. And the only way ik to fix this is to reinstall the game. But I'd be waiting a long time to redownload it. And it would get bad in a few days again. Does anyone know how to fix this? I definitely have the specs to run this game at 100+fps on 1080p. But fps drops even on 900p with 50% 3d resolution after a few days.