Windows 10: Why does my Laptop slows down very badly

I had a windows 11 installed laptop. It was doing actually pretty good till this January. I even played Valorant on it without any issues. After January, my laptop suddenly started to lag very badly when i opened up a game. It starts normally, goes on pretty smooth. But in the middle, it will lag out. After some time, it even creeps up to Normal usage. Nothing is listed on the task manager as consumptive. Even task manager takes a lot of time to open up. Then I completely installed a fresh copy of windows 10. I stopped playing all the recent titles. I'm playing Need for Speed Most Wanted. The

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HELP! My Laptop has gone into SLOW MOTION!

Should be able to get a "step-by-step here;

http://support.dell.com/?~ck=mn

 

Best laptop under $800??

Well the last one I suggested seems to be the best for 650$

EDIT: to facilitate your search...

Laptop GFX benchmark list

Laptop CPU Benchmark list

 

Constant script errors and slow loading pages in 10 internet explorer 11

I have done the steps listed above. They have not helped and I am still getting constant script errors, along with slow loading pages. Are there any other suggestions?