Ventilation system - General questions about ventilation and maintenance

[*]Bedrooms are ventilated for about 10 minutes in the morning after getting up and about 15 minutes in the evening before going to bed
[*]Bathroom after showering/bathing
[*]Living room with open kitchen during the day as needed

1) We are building our semi-detached house (approx. 120 sqm with basement, ground floor, upper floor, attic) "only" according to the 2016 Energy Saving Ordinance and I am now a bit unsure whether we need a ventilation system because today's houses are completely sealed. Our current ventilation behavior is, I think, the classic one:

[*]Bedrooms are ventilated early after getting up for about 10 minutes and in the evening before going to bed for about 15 minutes
[*]Bathroom after showering/bathing
[*]Living room with open kitchen during the day as needed

Is this ventilation sufficient or is it likely to cause mold in a sealed house?

2) If we decide on a (central) ventilation system: What about maintenance/cleaning? Our future house has ground floor, upper floor, and attic with rooms to be ventilated. If we put the system in the basement, that will be quite a few meters of ductwork. How do you keep them clean? I don’t want the system to constantly blow deposits/mold into the rooms after a few years...

3) If I understand correctly, the air balance between rooms with exhaust air and those with fresh air is achieved through the door gaps. Isn’t that a relatively strong airflow? Unfortunately, my wife is very sensitive to that.