Press and Hold volume uP + home + Power key
wait until you See the android Logo then release all the Buttons
now you see recovery options
now select wipe Data / Factory reset with volume Down key
Press Power key to Confirm
now Select Yes - delete all User Data with Volume Down key
Press Power key to Confirm
after format all User Data Press Power key to Reboot Device
press and hold volume down + home + power key
now press again volume uP key to Enter download mode