While the previous planning stage was accurate to a quarter of a decimeter, the execution drawing used real dimensions of the masonry walls. The wall between the children's rooms was not clearly identifiable before; now it appears to have been built. It is presumably bracing but not load-bearing, meaning it can be moved. So that the larger children's room does not lose its balcony door with the maximum possible reconsideration, I would leave the new wall standing up to about the desk and then bend it into the line of the staircase boundary wall. This correction should be done free of charge for you. You will have to live with the remaining small size difference. However, even twin children do not find this so bad. Do I understand correctly that the design is a self-planning, and you only gave it to a planning office for compliance drawing and subsequent tendering / awarding?
Das ist schlicht falsch. Verschobenes Fenster, verschobene Innenwand, ist für die Baugenehmigung irrelevant.
That is simply wrong. The shifted window is not relevant, but the room volumes for the heating load calculation also shift with the interior wall. The static remains unaffected for a non-load-bearing wall.