How do you deal with water condensation on the windows?
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?
You have to adopt the concept of "stosslüften" to get rid of excess humidity in your room. Warmer air carries more water, but it condenses on cooler surfaces Like outside Walls or Windows, the Window is the better Option because wet Walls get moldy soon. You also should make shure that there are no big furniture or other items without space to an outside wall if the building ist Not well insulated.
The issue is that you typically don't have any excess humidity in winter. Health wise you want 40 to 60 (or 50 to 60, depends on the source) percent humidity are ideal and with a lot of ventilation you'll quickly drop below that. Hence you might actually want to think about adding more humidity to the air (e.g. with plants or a humidifier).
Get a swamp cooler. They are cheap and effective. You can also makeshift one by putting a wet towel in front of a fan. And get a humidity meter they cost like 4$.