Gets hot.

[Saran]

Phone gets hot during these scenarios. 
1. When taking photos(as a back camera ) , the camera module's top side gets incredibly hot. 
2. When in a call conversation, the speaker side on the front of the screen also gets hot. 
3. And also It's been 20 days since I bought this phone, for the last 3 days, the phones getting pretty hot even using moderately. 

[Anders_ASUS]

1. This is normal. Our camera doesn't get warmer than on other phones internally, but since the exterior is made out of very conductive metal, you notice this much more than with a normal phone.
2. Most phones get hot during long phone calls. Your head is pressing against the phone, partially isolating the heat. 
3. You can download an app like 3C Toolbox and see which app that consumes more CPU/power than you think. https://play.google.com/store/apps/details?id=ccc71.at.free&hl=en