Put bg that appear at the mask disappear

Hello! How is it possible to put my background (that i already have behind the person objget, disappear, if, for example a face (so a face mask) is not recognized any more?

For example if i go at a part of a camera and i turn the face, the program removes the face effect/face mask, so i want, if this happen, to make all background, over the person, in order to not make person seen. How can i do that?

I see lens that does this, but i can't find anything on internet.

Thank you