Thanks, that is exactly what I was looking for 
So for everybody who is facing the same question:
You need one web application and as many process applications as you like. They should all use the same database. The web app calls the forms of the processes via a configured proxy. Stuff like listeners can be called, if in the process the task is asynchronous before. That leads to a job entry in the database and the web application knows what to do.
Pretty cool stuff 