Remove the handle.
Remove the plug that covers access to the corner trim fastening screw.
Unscrew the screw and remove the corner.
Remove the two screws securing the rear view mirror to the bracket.
Installing an outside rearview mirror
Installation of the outside rearview mirror is performed in reverse order.
Rear view mirror details: 1 - rear view mirror inside 431 857 511 B; 2, 3, 4 - outside rear view mirror 443 857 501; 5, 6, 7 - external rearview mirror with electric drive 443 857 501 B
[Information obtained from this resource AudiManual.ru]