Client scripts slow down Issue

I lowered Roblox’s window and used another program. This slows down all client scripts. This happens sometimes even if you don’t use other programs. Another problem is that the speed of Wait() and Run service decreases dramatically depending on the frame rate of the computer. It’s like an engine problem. How do you solve it?(I posted video too.)
Video Link(Video was big and i used streamable): 2021-01-23 17-20-30
Edit: I added one more video(Not lagging client video)
Here => https://streamable.com/tens11

Thanks,