why is all my apps crashing ?

[Android Central Question]

I have a reconditioned Samsung galaxy s7 that I bought 3 months ago. after a while all the apps started to crash to fix it I tried to reboot the device but upon rebooting it freezes on a black screen with the Samsung logo flashing. I tried to clean the cash data but that didn't help so I did a factory reset and that fixed it for a while but it happened again and I can't keep on resetting it.
also worth mentioning that I have this notification telling me that "unauthorized actions have been detected" as soon as I reset the phone and it never goes away.
how can I fix it?

 

[B. Diddy]

Welcome to Android Central! When you say you tried to clean the cache data, do you mean you wiped the cache partition? https://support.t-mobile.com/docs/DOC-30240

Does this also happen in Safe Mode? https://support.t-mobile.com/docs/DOC-28008