I was lucky enough to get help from a friend who really knows his stuff about this and he opened my eyes. There are really just three sources I recommend because I simply do not know anyone else who shows that:
ReadTheMarket (there is a topic by them on ForexFactory that explains most of it. However, be warned, the explanations are often shallow since they are making money by teaching others for a huge amount of money).
And Chris Lori (on YouTube). He explains the simple stuff that I trade super complicated since he is looking to sell his own course. In order to sell, it gotta sound complicated right?
And myself. However, I am not a good teacher and never really had the chance to teach someone but I am also not interested doing it as of now.
Hope any of these sources help you understanding orderflow. If you master this, I can assure you a high winrate with insanely high RR (1:20 and higher).