Android after dropping to the factory started to blunt, what should I do?

Question

Android

An old mobile phone with 512 MB of RAM was a little dumb. I decided to reset it to factory settings, it will be better, but in the end, now it freezes tightly, reboots itself and something else, what can you tell me ?.
As I noticed, there is very little free OP how to free it without a clue ..
There are root rights on a mobile phone, only if you need to do a lot of actions, then alas it will be too difficult :D