Yesterday I received the mail I was waiting for. Like I said before, I was taking the BPMN course of Bruce Silver. At the end of the course you get 2 exercises you have to solve and return to Bruce. After some hours of puzzling and drawing diagrams I came to an acceptiable solution (in my opinion) and sent it to Bruce. Although the first attempt wasn’t correct I received the response yesterday that the second attemp was a correct solution. So now I may call myself a certified BPMN consultant :-)