Galaxy alpha heating after purchase topic

I have bought a galaxy alpha four days ago. The device was working very well the first days with no problems. Excellent phone. It was getting warm, but I know this is normal for phones.

However the warm became worse, at the point the display was heating so much to risk to burn my finger. The display is now constantly getting warm even when doing simple tasks (whatsapp, browsing internet) and it is uncomfortable to use.

If I try to do a intensive task (like playing a game), even only for a few minutes, then it becomes hot and it makes the display almost untouchable. The top part of the display is especially affected by the problem. The back cover in plastic is also warm, but nothing that prevents me from safely holding the device in my hand

I have tried to turn off the phone and let it to cool down. However, after turning on the device again, the phone gets warm like before.

Is all of this normal? I'm aware that every phone becomes hot with use, but I believe my alpha is exxaggerated. I think it's a problem of faulty device, but I'd like to know your opinions first before to go back to the shop.

Thank you for answering