This circuit looks incorrect to me. I'll give you my recommendations but they are based on the following (please verify before rewiring anything!)
85 is ground
30 takes input voltage (ignition wire)
86 triggers the relay when energized
87 is energized when 86 is triggered
87a some relays have this additional connector, it is not used here, if you have it you should cover it to prevent a short.
With that in mind connect:
86 - BMW reverse light pulsating wire
87 - to Video Module backup trigger
85 - car ground bolt
30 - switched power
Your camera should have the positive wire connected to a switched power supply and the ground wire to the ground bolt if possible, otherwise it is generally okay to use the most convenient ground wire.
I have an aftermarket radio in my X and have been using this setup for my camera for years.