thanks for your help everyone who helped me get through that problem, i started a new game and managed to get to Chernobyl NPP in less than 10 hours in one day (lol, im cool)
completed the game just now
i took ur advice and turned lighting to static instead of full dynamic and the levels were really smooth, even the brain scorcher with an average FPS of 160.
I went for the false ending "i want to be rich", i cant be bothered to go for the true ending, i seen it on youtube anyway, lol
i just saw there is gonna be another stalker (clear sky) so cant wait, i hope they include more levels like pripryat - that was amazing going through abandoned flats and seeing the infamous ferris wheel

(wish i had more time to explore it)
again, thx for help in making rh game work for me