Frame rate gradually declines after 5 min + Audio distortion.

Need some help, 

Firstly i've updated all drivers, reinstalled the game (Steam), googled and read many many threads and i can't find the solution.

Laptop
I-7 4700HQ CPU @ 2,40 GHz
8 GB RAM
GTX 760M
Windows 8,1

So after starting PoE it takes about five minutes before the game starts lagging, stuttering and it gradually becomes worse. When this happens the audio gets spikes of distorted sounds when other sounds are playing like conversations etc. it sounds a little bit like the speaker is broken. 

It only gets back to normal when i restart the computer and then i can play 5 min again before the problems start. CPU is at about 13% and about 1 GB RAM usage. The Laptop becomes very hot when i play PoE, It's not even remotly this hot when i play other games like Dark Souls 2 on maxed graphics.. I've turned off the anti aliasing ingame but no change at all. 

Has anybody the same problem or does anybody know how to fix this?

I'm kind of a noob when it comes to computers so please explain like i'm a three year old.

Regards