I upgraded my car stereo to KitKat now I have no sound and nav. How can I fix this?

[AC Question]

I upgreaded my car sterio to kit kat now no sound and nav

I received an up grade from china. Followed directions all screens came up as directions said. But now there is no sound and when I try to bring up my navigation it goes straight to Bluetooth. Is there a way to go back to factory standards?
Android 4.4 6.2
Android 4.4 6.2" Double Din 3G-Wifi Car GPS DVD Player BT Indash Radio + CAMERA

 

[Rukbat]

Get a flash tool and 4.4.2 or 4.4.4 ROM image from the manufacturer. Back everything up (see Backing up an Android Device). Flash the older ROM. Restore everything.