Can you list your system specs?

Can you also list what settings you used in game?

Can you explain exactly what is going on within the 20-30 minute window? Is there a certain map that you are exploring at that time or does it occur randomly? Is your computer overheating causing it to thermal throttle?

The more information the better.

It seems like a memory leak in the game, happens to me too on a 5070ti, 7800x3d and 32gb ram

That could be a memory leak from a driver issue but that could also just be the beginning area running easier because lighter and not having as much surroundings and ennemies as the rest of the game. Once out of the train station it should be pretty similar to how the the rest of the game will run

If you restart the game there or later and instantly have 20-30 fps you may need to look for graphics settings to turn lower, if you have background softwares taking unecessary calcul power, etc.
If you are on a laptop, check the power mode/energy saver in Windows' Power settings. Sure the battery will empty and use quicker on higher mode but that is laptops' issues with gaming

引用自 sehun77：

I installed the old nvidi driver 573.83. and it seems to have helped, for an hour the fps stayed at 60 hmm

I Will try that to see if it works

İt actually worked thank you my guy