Instruction I:
1. Turn the display on.
2. Now press'n'hold the Power & Volume Down buttons for a few seconds.
3. Release these buttons after the phone vibrates and resets.
Instruction II:
1. Hi. Please, remove the phone's back cover and battery.
2. Spend five seconds on contemplating the beauty of the world. Afterwards, put the phone back together and press the Power button. Well done, the soft reset is complete.