* press and hold together Volume Down and Power key for a few seconds.
* You should release Power key as soon as the Oppo logo appears on the screen.
* Release Volume Down button as sonn as the Language Menu appears on the screen.
* In this step select English using Volume keys to browse and Power rocker to select.
* Then select Wipe data and cache twice.
* Confirm the whole process by selecting Yes.
* In order to restart the device tap Reboot.
* Well done! The hard reset operation has just been performed.
How to Hard Reset Oppo F1 Selfie Expert
read it. http://www.hardreset.info/devices/oppo/oppo-f1/
