My phone is hanging and automaticaaly shutting down

You can use Wondershare Mobilego to back up everything first before HARD RESET the phone:

Hard reset by:

Turn off phone completely

Hold Volume Up and press Power

After phone turn on, keep holding volume up and release power

You will enter a screen where there is an option to wipe everything

Navigate: go up and down by volume + and -

enter by power button

The hard reset process are mostly the same for every android. If you find yourself unable to access to it, you can reset the phone in Setting > Back up and Recovery > Restore everything (or something like that)

Hope you find this helpful.

P/S: If you have done hard reset already. You can bring to a phone shop to do hardware/ firmware repair. If you don't want the trouble just back up data and get a new phone.