I did some research and probably my dt was  to big. With 0.001s I had the best "results" yet but in my case I might need to reduce dt even more. The minimum cell size is 2x10-5m and the maximal cell size is 0.065m. So I am trying to simulate with the "Adaptive Time Stepping" method and I am getting a physical dt varying between 1x10-5s to 5x10-5s (inlet velocity of air is 12.6m/s). At the end I will have a solution with a flow time of maybe 1s if I iterate 20 000 times... Not good not terrible