Default [Q] Help please. Doogee dg550

Hello, i bought a new Doogee dg550 from
I am from Lithuania, and he came in my hand today.
So the problem is, when i turning it on and he boots, when i start using it, internet browsing, gaming (asphalt 8) , he working for a little time. But in the screen appears the message:mtk thermal manager, thermal warning phone needs to cool down and he shutting down. Then i start it again and using it about 10-15 minutes the message appears again. But the phone is not hot really. So where are the problem?
Please help me i love this phone design, menu, and speed, but that problem leads to despair.
I am waiting yours answer.
Thank you very much.