Cubot One Super Slow without reason?

[AC Question]

Hello. I have just got a used Cubot One. It is an original phone, and it is lagging so much that i can't even play subway surfers. When i open the "System Info" app, it is telling me the specs (Quad Core, 1GB RAM) and when i test on antutu i get score 19k. I tried to factory reset or clear cache (I ever tried to flash back the stock ROM).
It is even lagging when i try to type.
What could the problem be? Could it be the battery? Processor? What?

 

[B. Diddy]

Welcome to Android Central! Try booting into Safe Mode, which temporarily disables all 3rd party apps. On most Android devices, while powered on, press and hold Power until the Power Off menu appears. Press and hold the Power Off selection until the Safe Mode prompt appears. Tap OK.

If the problem disappears in Safe Mode, then something you installed is causing the problem. You may have to uninstall apps one by one until the problem disappears. If the problem persists in Safe Mode, then it's more likely to be a hardware or firmware problem.