My phone is running really slow and keeps turning it's self off then I can't put it back on HELP

[AC Question]

I have a Samsung note 4.
Which keeps turning itself off.
Freezes. Tuning really slow .
I have reset back to factory settings. Still no better. Brought a new battery still the same.
Dont no what to do now.
Is my phone beyond repair.
help

 

[B. Diddy]

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