Hard Reset HUAWEI UM840

First method:

1. Turn off the device.
   
2. Hold and press Volume Up + Power button for 10 seconds.
   
3. When logo Android is appear, then release holded buttons, and press Power button.
   
4. Next please navigate to "wipe data/factory reset" using Volume Upto browse and Power button to confirm.
   
5. After that wait for phone to restart.
6. Success!

Second method:

1. Power on your device.
   
2. Next from the Home screen select Menu.
3. Now choose Settings -> Back up and reset -> Reset device -> Delete all.
4. Confirm all informations, and wait until your phone will reset and reboots.
5. Success!

WARNING !
Hard Reset will erase all of your data
All described operations you are doing at your own risk.