ᐅ Condensation inside the frame of new wooden windows

Dear forum members,

I hope you can give me some advice on the following issues:
Last year, new wooden windows were installed in my 1950s old building. The entire building was completely renovated. The upper floor was fully insulated according to KFW standards, while the basement, supervised by a thermal insulation specialist/structural engineer, has no insulation but slightly more "permeable" windows.

Now that it is freezing and even last year, there have been recurring issues with water standing in the window frames. According to the window installer/joiner, this is not a problem, but it worries me.

The windows are properly adjusted and sealed. I have already tried adding an additional seal on the inside, but then the windows no longer close.

Does anyone have any advice? I would be very grateful as I am completely inexperienced here…

Also, on the seals of the casement doors, there are small white plastic plates. Are these necessary? Most of the windows do not have them.

Can you slide a sheet of paper through when it’s closed? Yes, adjust it regardless of what the window manufacturer says.

Yes, I had thought about that too. But I have to press the window firmly to close it properly. The sheet of paper stays firmly in place…

Condensation from showering and cooking? What does the hygrometer say?

Probably kitchen and bathroom? What is the room temperature?

This actually applies to all rooms on the upper floor. I have set the room temperature to 17-18°C (63-64°F). Some of the rooms are still not occupied yet.