Slow as a snail

Today my pc froze suddenly. I restarted my pc and the reboot did go normally. But when I try to start a program, it will start very slowly and when you try to interact with it, the program will go in "Has stopped working" mode.

Some notable things:
I can open the start menu, but when selecting a program it stops working.
RAM usage for a program that starts up, climbs very slowly instead of normal speed. (chrome can take 3 minutes to start)
When a few programs stop working, the task manager will sometimes stop too and then the pc will no longer respond (cursor can still move, ctrl alt del doesn't work)
Everytime I start and close the program it seems that it starts a bit faster each time I restart the program, just a bit but that's not good enough for practical use.

I also have a video in which I started a video game while monitoring the RAM usage.
https://www.youtube.com/watch?v=Xyfb2OsgT_g
The game was at 200MB RAM after 10 minutes, the game supposed to start at 800MB within 1 - 2 minutes normally.




I have this pc for 2 years now so specs isn't the case.

Can anyone help me with this? Because I can't use this pc properly.