Laptop overheated...

Hello,
i have a problem with the temperature of my laptop. It's an Acer Aspire 5920G.
It just started a couple of months ago. When the ventilator was making a really loud noise. Then i think 15 minutes later my laptop feels really hot and the ventilator spins like crazy.
The laptop gets really hot especially when i play a game.

The laptop is not really that old, it's actually quite new, but i think a month after buying it i already had that problem. So if someone knows the problem or knows how to repair it i really appreciate it.

Greets,
Javi