problem with fps issue in new map

hello!

before explaining about my problem, I'm sorry for my english.

I'm using 144hz monitor and my pc specs ryzen 5 2600 gtx 1660ti 16gb ram.

when I'm playing with 144 fps but I sometimes get some fps drop 144 to 100 or 110. and I'm really getting laggy and really not smooth. tried v sync  rtss and etc on internet. I still cannot fix my problem and it effects my performance in game. maybe u guys know any solution for this? I'll be happy to try. thank you !