help please with gta v lag ??

i have amd 8850 2gb GDDR5 , RAM 8 gb , processor i7-4500U ... the game is stuttering even if i play in normal everything in normal !! i tried to use radeonpro but i don't know actually how to use it and set good settings but when i use it i got in the game FPS from 20 - 30 .. whats the solution ??

help please with gta v lag ??