-Backup your internal storage data
-Boot to recovery
-Format Data (It's must.)
-Reboot to recovery
-Connect computer to your phone and copy all above files to phones internal storage. (A11 Firmware, ROM, Gapps.)
-Flash A11 Firmware
-Flash ROM
-Flash Gapps (Nik Core recommend. If you want Google restore then use Setup_Wizard addon.)
-Reboot
Que es eso?