How to Hard Reset Samsung Android Mobile Phones 

Problem 1 : Stuck At Samsung Logo Screen

If you screen is frozen or you could not turn on your phone. To perform a factory reset using 
the 'Recovery Mode'. This all so format your phone memory.

1. Hold the Volume up + Home + Power key at the same time

The Android recovery mode appears, select: wipe data / factory reset with the volume keys

Enter with the power key. Then restart the phone. mobile phone fully formatted.

Problem 2 : Slow Running and hanging 

simple device resetting 

Apps -Settings - Accounts - Factory Data Reset - Reset Device - Delete