Steps between kitchen/dining room and living room

I would definitely keep that as an island. You have enough floor space at the bottom of the plan, and it’s nice when a kitchen island can be walked around. And 240 cm is absolutely sufficient if only one functionality (cooking or washing) is planned. I am more of a sink-island fan, because then you have the free choice of extractor hood and can, above all, install a good ventilation solution on the wall unit via a short distance.

Congratulations on the architect. I'm looking forward to the rest.

The drawback is that we have little space in the dining room for a comfortable seating and lounging option for the children.

You could also consider a seating window

You could also consider a seat window

I have thought about that too and I would really like it. I just don’t really know where. Two sliding doors are planned, after all. Rather on the south side or out back to the larger terrace...

I find the visual connection between Ko/Ess + living very important, as I would like an open and coherent living space.

Then please plan the new building not with a clear height of 2.40 but rather with 2.80 or 3.0 m so that you don't look against the lintel from the living room, but can also look out into the garden.

Then please don’t plan the new building with a clear height of 2.40 but rather with 2.80 or 3.0 m so that you don’t look against the wall lintel from the living room, but can also still look out into the garden.

That was actually my wish, but the architect said that the extension would then look disproportionate and not visually appealing. Since the extension goes around the house, 2 side windows would have to be reduced in size, but that would be okay with me (one will probably be removed anyway). However, I think that an increase of 0.40-0.60 m would also not be enough to see into the garden. Then you would almost have to go to the same ceiling height, right?