Process and UI system not working

[Android Central Question]

Hi, I have a Nokia 3 and recently it has been paying up and freezing etc but this morning I unplugged it from the charger and had various system messages that the processing system and system UI had stopped working. I have tried turning it off but nothing happens,even when I have held down the power button for a considerable amount of time. This is rather important as I am a student and need my phone for information and deadlines. Is there anything else I can do? I have even tried taking the SIM card out and replacing it but it just keeps the same messages popping up and I can't get rid of them or fix it. Any help would be appreciated. Thanks