Inspiron 15 Gaming 7577 huge fps drop

hi guys! i know that had been similar posts. but i coudnt figure out.  so i have this laptop , 16 gb ram, with  ssd 256gb, ,  gtx 1060 ti  6 gb,  i5 2,5 ghz. i have  it now for 1 year. everything perfect until now, games ruled on high and ultra pretty good. but from a period, i have big fps drops. to 20  30. on nvidia on optimal settings, it makes on ultra for settings.before i had almost 100-120 fps, it drops every minute.  i instaled windows 2x times. install all drivers. checked for errors. nothing. in dell assist everything is ok, for every test .the laptop is not heating to much at all, cuz i use a good cooler. . i tried setting to best performance on power,  and from nvidia ct panel, on maximum performance. i did all the stuff that i fount on internet. nothing worked. any tips?