Hard Reset HTC Desire 816G Dual SIM

First method:

1. At the beginning turn off the phone by using the Power button.
2. Afterwards press and hold Volum Down and Power buttons together.
3. Wait for the three Andoid images.
4. When you see them, choose the Factory Reset by pressing the Volum Down button to selecet and the Power key to confirm.
5. Success! The hard reset is done! 

Second method:

1. Turn on the phone by using the Power button. 
2. Go to Settings and then to Backup & Reset.
3. Tap Reset Phone. 
4. Choose Erase All Data if you are sure you want to clear all your data. 
5. Tap OK. 
6. Well done!

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