Financing / cost estimation that realistic?

Fire preparation, electric roller shutters, door between garage and utility room, adjusted shell construction height, heat pump, additional shower in the guest bathroom are already included in the cost estimate.

When building, not only the bullet point matters but also the execution itself. A shower can look like this or that and cost more or less accordingly. Heat pumps range from "low to high." Many euros are involved in the details – just keep that in mind.

Since we actually planned to wait at least another year, many of these things have not yet been finalized, but we are now dealing with heating, photovoltaics, controlled residential ventilation, and the chimney. Currently planned is a Kfw55 solid house without a basement as a city villa; however, we also like the charm of a gable roof house with a high knee wall to achieve 2 full floors. Of course, it is then questionable to what extent the attic can still be used for storage with a roof pitch of 25 degrees and whether this is possible with a maximum ridge height of 10 m and an eave height at least 1.50 m lower than the ridge height (requirements of the development plan). We would only enter into more detailed planning with the construction company then and could possibly build in the fall of next year. The construction company has a total of 17 plots and develops them on a First Come, First Served basis.

I did not understand why less storage space should be created under a gable roof than under the Stadtvillahütchen. Either way, you will not be able to move upright much in the attic. Storage space is created by the area. Say goodbye to the ultra-comfortable accessibility of every single item. Much of what is stored in attics is not used for years. The other things simply get a logistics-prominent place. Do you already have an overview of what is supposed to go into the attic?

We generally don't have a lot of stuff and even in the rental apartment the basement is almost empty, so I expect at most 3-4 storage boxes with seasonal decorations and later with stored children's clothes/ski clothes but not more than that. It was probably more my thinking but true, under the little city villa roof there isn't much either when all four roof sides slope down.

Have a look for fun at the rail systems with costs for the rear garages of motorhomes. In this area, people know very well how to optimally use hard-to-reach space. The freight yard under the roof - worth a DIY idea.

Are there any other tips on what we should tackle directly and next, and what is coming our way?

Unfortunately, we are really unsure whether we should dare to do it now in this situation (probation period, little equity), but I think only another conversation with the construction company can clarify whether they can (and want to) push us back from the 17 builds to gain a bit more breathing room.