Hello,
I see that you have not put the A20 Pro model on the forum list! and I have to post in the A20 model!

I buy a Blackview A20 Pro, since the update of Oreo I no longer have the camera function Video, I only have the photo function, yet when unpacking and running the smartphone the video camera function worked, and the bar of the spots of the top which indicates the reception of the signal, the wifi, the bluethoot its become small icon I thank you for giving me explanations like for example to find the function video camera, or to find the biggest icons of the bar of the high signal sim card, bluethoot, wifi
cordially

Hi there.
Just perform a factory reset from the recovery menu and all issues will be fixed.

Follow this link:
viewtopic.php?f=192&t=334922