x17 R2, huge fps drop

I have an x17 R2 (RTX 3080 Ti, core i9, 2TB, 32GB ram). I would like to say that my laptop has a huge fps drop when I am playing some games. Like for example Fortnite I play on 200+ fps for at least 2 minutes and the fps instantly drops to 20fps for the rest of the game. I find it really challenging to play on 20 fps mostly relating to the fact that I had bought the laptop expecting to get good fps for gaming. So I would kinda like you to help me sort the problem.