To factory reset your phone, follow these instructions. All your personal data will be permanently erased.
Turn off your phone. Next, press the Volume down + Power buttons at the same time. Once it turned on, go to Recovery mode by using the volume down button.
Press the Power button to restart the phone in Recovery mode. The screen will display the Android logo with a red exclamation mark, press the Power button and the Volume up buttons and release them.
Go to Wipe data/factory reset by using the Volume down button. Press Power to select the option. Then, choose Yes - erase all user data.