FPS drops after an hour of gameplay

any fix for that?

getting nice and stable 60 fps on my laptop then after an hour of playing shader bar gets maxed out and fps drops to 15 fps, restarting game fixes that

Unless you have run of vram (unlikely), the probable culprit is the infamous windows defender.

If you're using nVidia graphics, this is a common problem as the game maxes out the shader cache and causes the game to temporarily freeze as it recompiles shaders.

Use the nVidia app, go to Graphics -> Global Settings and set the Shader Cache Size to a higher amount (10GB or 100GB).

Still, it's best to restart the game every few hours to keep things running smoothly.

I've seen some posts that say switching between DirectX12 and Vulkan can prevent some crashes.