- Make sure, that your phone is off.
- Now press and hold Volume Up + Power button until you see Android green man.
- Then select language "English" from the menu.
- Next choose "wipe data/factory reset" using Volume keys to scroll options, and Power button to confirm operations.
- After that confirm operation "Yes" using Volume Down button to browse, and Power button to accept operation.
- Afterwards select option "reboot system now", and confirm with Power key.