I figure out that wehn steam wallpaper changes.The game will slow down. I think this is a GPU problem. Could anyone tellme how to solve it?

Wallpaper engine uses RAM and GPU power to run so it can effect the game you're playing especially if your wallpapers are animated. I personally have Wallpaper Engine set to pause when a program is fullscreen or maximized. In settings look under "performance" and then take a look at the options in "playback" and see what would work best for you. I'd recommend using "pause" or "stop" for the option that says "other application fullscreen"

The easy or quick fix would just be to disable Wallpaper Engine while you're doing speedruns.

Thank you.Now I have changed a GPU(AMD6950).It works better.And also,I can close the wallpaper engine

By the way:Is there a wall paper with a theme of Stray?