Laptop Shuts Down When Playing Games :(

Hello

Well i bought a new dell laptop inspiron 15 5000 series 5559, it has 2 graphic cards, intel hd 520 & amd readeon r5 335
When i activate both cards i can play with amazing performance, but play for around 5-15 minutes & then my laptop shuts down, however when i use only intel HD graphics 520, & deactivate the other one from device manager, i can play normally no shutting down, exept it costs FPS & performance, Please answer quickly i cannot take it anymore, also i updated my BIOS & reinstalled amd drivers 

Thanks for taking your time reading this & i hope you take a little bit more to type the solution if you know it

Thanks, Have a nice day