high end PC with bad fps in CSGO

[Cancerkid]

I have a gaming pc with a asus gtx 1660ti dual oc(not oc), an intel core i7 8700k (not oc), a corsair mp510 128gb ssd, 2tb toshiba hdd and corsair vengeance rgb pro ram 16gb (not OC) . Back then i used to get about 300-400 fps when my pc was new, and now i get much lower at around 150 to 90fps at all medium 1280x1080. I tried a couple of solutions, like dowloading razer cortex, but when i did that it causes like 2 seconds of input lag but the fps was normal again, so idk what is going on here. It's also especially bad since i have a 144hz non g-sync monitor and it makes it look terrible when i go below the refresh rate. I also checked the thermals and none of the parts every even went above 65 degrees celcius while gaming, i also checked that the clock speed of the gpu was going up and down(idk if thats normal). I check the percentage use of csgo and it matches with other people, i checked other more demmanding games like beamng drive and the clock speed was basically stuck at 1900mhz, and i also retain around 110 fps, i also tried other less demmanding games (i think they arent that demmanding) like minecraft and simple rockets 2, i got pretty low fps on them with minecraft with no shaders getting around 50fps and simple rockets with the same fps. I need help with this please im just a dumb 14 year old child who watches linus tech tips daily.

[Cancerkid]

also my monitor is in 1920x1080 and hyper threading is on. 

[Enderman]

Reinstall windows?