Hi,
Try to factory reset it.
Press and hold Volume Up and Home button. Keep pressing them, pres Power On button. After 2-3 sec. release power on button but keep pressing VolUp+Home.
When you see Android recovery menu, use VolUp and VolDwn to navigate in the menu and PowerOn for OK.
- wipe data / factory reset
- Yes, erase all data
- reset
!!! This operation will erase all your personal information !!!
Regards.