If your 6 volt is connected to the ESC, then it should be providing power to the Receiver and the servo. Do not connect a separate battery to the receiver. I am not familiar with the Graupner ESC, but will look it up and check it has a battery eliminator circuit. (BEC)
Ill add to this when I've done some research.
I've checked the V40R and it does have a BEC so you definitely do not need a separate battery for the Radio and servo. The following sketch shows how to wire up your model.
I've shown a switch in the positive lead, but this may not be needed as I think I read that the ESC has a switch. You should really replace the switch with a Fuse with a value less than the maximum rating of the ESC. Car type blade fuses are suitable.
The ESC seems a little over complicated being programmable, but should be OK. What is your model?