Build a terraced end house with an additional unit (GÜ) on your own

I also think that there is still time until moving in to consider what you want and that there are still enough other topics inside.

I also think that there is still time until moving in to think about what you want, and there are enough other topics inside.

Actually not.

Electricity: currently ongoing
House connections: water, electricity, and telecom all running
Sanitary: heating & ventilation system done, ceramics and bathroom furniture chosen
Kitchen: purchased
Flooring: all decided
Stairs: sampled and everything discussed
New furniture: 50% chosen
Outdoor area: just started

As I said: we need our parking spaces when we move in. Therefore, I inevitably also have to take care of the terrace right away.

Also: apparently no one in our region feels the need. One landscape gardener said on the phone the other day that he works based on personal sympathy – or they simply don't get back to you.

Besides, I don’t want our little one to fall 1.50m deep into the garden when I open the terrace door after moving in.

that may all be true, but as long as you don't know exactly what's happening there, it may be that you will have to deal with things twice. Parking spaces in the front can, in my opinion, be considered separate from the garden or a clear "cut" can be made. Sometimes it is really worth waiting and taking a good look at everything and thinking about what, how, and where things should take place in the garden. I speak from experience

Then you just wait a season.

Joker. It’s not about waiting for perfect bloom, it’s about mud in front of the patio door, or in this specific case, about mud also on a one-and-a-half meter slope in front of the patio door. With the detached neighboring house, that would all be a private matter, but in the row house, it seriously disrupts the neighborhood dynamic.

that may all be true, but as long as you don’t know exactly what’s happening there, you might have to redo things twice.
Parking spaces at the front can, in my opinion, be considered separately from the garden or a clear "cut" can be made.
Sometimes it really pays off to wait and take a calm look at everything and think about what should happen where and how in the garden.
I speak from experience

We definitely won’t rush anything. However, we certainly won’t be able to leave the house as it is when we move in. In the worst case, we’ll pile some cubic meters in front of the terrace door to at least have a height adjustment and an improvised seating option. That is my wife’s minimum requirement.

at least some height compensation and an improvised seating option. That is the minimum requirement of my wife.

She communicates this best directly to Frau Mittelhäuser