I found the solution myself!
In Realflow create a scene and run the simulation.
After the simulation has finished save the project and close it.
Then create a new Realflow project and drag a NBinary Emitter into an empty scene.
In the NBinary menu load the particle folder from the previously created scene, and set playback in reverse mode. The simulation from the previous scene now plays backwards.
Create the meshes and load the meshes in the ususal way into C4D for furhter processing.
Thanks for the help!!!!!!