Factory reset erase all data from your device's internal storage.
You have a problem with your device or you want to reset your device, you may use factory reset.
PM66
Press and hold Power + Volume Up + Front Scan buttons simultaneously when turning on the device
After short vibration, release the buttons. Now your PM66 is entered Android Recovery mode
Using Volume(move up&down) and Power(select) buttons, select 'Wipe data/factory reset'
After wiping the data, select 'Reboot system now'