[AC Question]

I've got Android 5.1 installed and have downloaded some sort of a virus. Very frequently a full screen add pops up that must be cancelled before you can use the phone. I've scanned with several free-anti-virus that don't seem to find any major problems (except cleaning out cashed etc.). I've also uninstalled everything that the phone will let me uninstall but that doesn't work either.
When I scanned with Malwarebytes it found 1 infection Android/Trojan.FakeUpdates.V However, Malwarebytes cannot remove the infection because it thinks the phone is rooted.
I didn't root the phone(at least deliberately - I don't even know what rooting means ). So I've checked if it is rooted with kingroot and another root-checker app that say that the phone is NOT Rooted
Also, the phone is now getting noticeably slower and the battery is suddenly failing before a day's use is up.
The phone has a 4500 mhA - V-Phone X3 - 6 months old
Could anyone please help solve this problem

[belodion]

Are you saying that you downloaded 5.1 from somewhere yourself?