User blog:ArchKnightUlthering/My Problem In Metro 2033

I have a problem in metro 2033 and it's rather weird after i have finished metro 2033 we bought a new PC with the following hardware: So the first game i installed was metro but it didn't work so i simply gave up and tried assassin's creed revelations and it worked out perfectly with the highest quality without a single problem and then Divinity 2 which was exactly like Assassin's creed and then many other games that didn't work well on my old computer like: Dragon age origins, Dead Space 2, Prototype 2, kingdoms of Amalur reckoning all of them worked perfectly on the best quality so i decided to give metro another try and it worked so i went to the options and changed them into the highest quality every thing was great but sometimes the game becomes laggy for a while of time like 4 or 5 minutes and then every thing returns normal the places i still remember are Chapter 4 front line, Chapter 7 top, and the child level, and i just don't know what is the problem!!! first i thought it was the DX because i had DX 9 and metro needs DX 11 but when i downloaded the DX 11 nothing has changed can you tell me what is the problem please.
 * 1) Core i7
 * 2) Cache 8 MG
 * 3) Video card 2 GB hd
 * 4) Ram 8 GB