The Asus A42J graphics card overheats and shuts my laptop down

2 or 3 years ago my laptop fell down and my fan became noisy after that , but it didn't cause any problem, it was just noisy, I was able to play any game I want.

but from a few months ago whenever I lunch a game it shuts down immediately, and after that if I try to turn it on , it will shut down again in windows boot up process . so I have to wait until it cools down .

and its not only games that causing my laptop to overheat, I can't use firefox for browsing because apparently it uses more graphical resources than chrome, and even with chrome I can't load some websites that have some graphical interface in them(like twitch or soundcloud), I can't load flash files, I can't open 1080 videos files,

I even replaced my noisy fan with a new one

anybody knows what is causing this problem ?

Edit: I feel like I need to add some more information,

1-My heat sink and fan are clean and new and there are no dusts on them

2-it's not software or virus related because even when I enter the bios setup before windows starts up it overheats and shuts down( so maybe the graphics card is not the reason of this issue after all :D)