Warning! All data will be lost after hard reset.Please make backup first.
1.Power off your phone
2.Press together volume up + home button + power button until you will se Samsung logo on the screen
3.Select with volume buttons "wipe data/factory reset" and press power button to confirm
4.Select "yes" and press power button to confirm
5.Wait until format is complete
7.Press power to confirm "reboot"
8.Wait until the phone restarts