very strange at least you should have 140 fps!
is the average of this graphics card "GTX 1660S" you having good processor.
What could be happening to your fps break?
Updating drivers on windows.
go esc, menu see if fps limitation
After that, if it doesn't work, I advise you to format your computer.
And the first thing, install your drivers manually on the website of your motherboard, first install cpu z it will tell you all the details of your computer.
After that you will have a new computer playing 140 fps more!