After your friendly replies i would like to give an update. I did play with phpbb and its really nothing to go these days. It feels like stepping 20 years back compared to the nodeBB user experience.
What i am doing now is to refactor my game on base of angular2 stack and to add a a very small forum like messaging feature myself. I think this will be the best solution because it seamingless fits into my application.
You are doing a great job here and if i ever search for a real forum again i will come back 🙂