Minor annoyance: Game performance drops after 30 min

Hello mostly new user here, I have a weird problem with deadlock(by valve). After a lite bit in a game (20-30 min) my fans drop and fps drops from like 165 fps to 15. I suspect its switching the governor or lowering do to high temps. I some times have my door closed and it can get a bit worm in my room. But when i open the door and it gets cold again it dose not change the performances. I have to quit the game and open it again to undo the hit to fps. Please help me =)

If you run mango hud or steam overlay what does your temps say?

74 on the CPU and 78 on the GPU

cpu thats all good, gpu could be the issue, what model?

I have a RTX3080ti

sorry for long time to respond.

I am sorry where do I put the (LD_PRELOAD=“”)?

Game’s launch options

What are those and where do i find them?

realy sorry

(Steam game) settings > properties