Now that the temperature outside has dropped, the windows start to accumulate water vapor. I am assuming that it might also lead to that black stuff forming. Is there a more efficient way of dealing with the condensate than wiping it dry every day?
Wipe it off in the mornings - Lüften alone will not prevent mold on the window frames. Lüften short and intensive several times a day.
Move to a warmer climate where that doesn’t happen? Or wait what’s in the climate catastrophe lottery for Germany - it may become much warmer in the future (not necessarily, depends on Golfstrom).
The other solutions (air dryer and the likes) are more annoying and much more expensive. It simply is the way it is.