Can't turn off phone

I would suggest first:

Do HARD RESET:

Take out battery

Hold volume +

Insert battery while holding volume +

Your phone will boot into recovery mode

Use volume + - to move up and down

Use power to confirm action

Your have to select action Wipe Cache/ Wipe all data

Second if first didn't work:

You need to re-firmware the phone

FLASHING INCOMPATIBLE FIRMWARE WILL TURN YOUR PHONE INTO A BRICK SO DO IT AS YOUR OWN RISK

_Get Odin.exe

_Get correct firmware from Tsar3000

(to get the most correct and compatible firmware get the model that match your country + original carrier)

Finally good luck: if are just amateur don't try second method brig to a phone shop instead to save your trouble