I am using Samsung Galaxy J7 from 1.5 years and my experience is worst using this device when I bought it it comes with android lollipop 5.1.1 and I had updated it to Android marshmelow 6.1.1 after that my phone becomes hell for me it gets many bugs and even for few days my phone screen is not working properly and after that my phone speed becomes very low, It have 16gb internal memory 1.5 GB RAM and have dual SIM support with 4gvolte and a slot for memory chip It have an axinox octacore processor but the phone lags so much.it has 3100mah removable battery initially it have a good battery backup but after 3-4 months it’s gonna be bad my phone is getting hot and it takes 2- 3hrs to get fully charged.It have a 13 mp rear camera and a front facing camera of 5 mp with flash which is satisfying on all the worse.
I suggest not to buy it. Go for galaxy J7 pro or j7 max they are much better options.