Hacker removal

My phone has been hacked. Someone is logging in as guest user while I am logged in as Owner. I have also caught them accessing my phone using Blue tooth, cast, and wifi Direct. Whenever I do a Factory Reset, the spyware installs itself as soon as the hone reboots. I have tried downloading security apps but they all say that everything is fine. In settings, I have blocked all apps from any access they don't need. Nothing I do can get rid of the spyware apps and unwanted guest user. A few of the spyware apps are: Fused location, Atforward, Motorola bug-to-go, shared library....