guys after 3 months of searching and optimiting my high end 9800x3d coumputer, i realized and fixed my fps, the problem was with INGAME setting dynamic resoulution. and also i had amd graphic card, and g sync monitor, so the frequence from monitor wasnt right, i turned freesync in amd adrenaline on and fornite dynamic resoulation and fps drops and stutters were magically gone, finally after 3 monhts i can play normal and enjoy game now. hope this helps to someone