Finally I have installed the rear view camera bought from aliexpress for about 40$, the mounting took me around 4 hours, I have actually passed the cables on the floor-luggage compartment to the right door sill cover strip and finally to the dashboard.
Actually I have seen many mountings that goes above the right windows underneath the trim, this is actually very dangerous , as there is the lateral airbag over there and nothing must be fixed above it (BMW documentation said so !).
The camera is working perfectly.