Weird FPS Dropping Constantly

Greetings. I've been having an FPS dropping problem since last month and it's never happened before.

The Steam in-game FPS visualizing keep showing like 4 or 5 FPS, right from the green gem start to spin. And it happens everytime when I launch the game, which totally unplayable under this circumstance.

I know there're few things could be causing the problem. My PC's not high-end enough or the image qualities are too high, I'm playing The Sims through Portable Hard Disk, some options under the Windows or NVIDIA is going wrong...bla, bla, bla.

But the thing is, my CPU is i7-9700 and my GPU is 2070S. Maybe some of the games could go under stabilized 60 FPS but 4 to 5 FPS for The Sims is totally unacceptable. Secondly, I play GTA 5 or Life is Strange Re and a lot of any other games fluently through Portable Disks. It's fine.

So I don't know what's going on. The FPS just drop massively everytime after the opening animation's over and starting to loads into the actual game. Need some help, and I'm much obliged.