A hard reset will erase ALL data on your phone, including apps, contacts (unless saved to Google account), photos, videos, music, and system settings. It will not remove the Google FRP (Factory Reset Protection) lock if you have a Google account on the device. How to Hard Reset DOOGEE S41 Pro
In the "Boot Mode" menu, use the Volume Up key to scroll to "Recovery Mode" and press the Volume Down key to select it. A hard reset will erase ALL data on