Affordable garden in new construction - how to proceed best?

It's quite simple. You take a long straight edge and place it on the base so that it rests everywhere. Then you take a spirit level with two vials (one 0 degrees, one 2 degrees) and if the 2-degree vial is level, everything is fine. Otherwise, you adjust with the shovel. And if you end up with 1.5 or 2.5 degrees, that's not the end of the world either.

Sorry, but these tips don't work here…
And it's not that simple again…
(I have to look up [Richtlatte] now ;) )

Uh, lawn as you plan it is pretty much the most maintenance-intensive thing there is. Mow at least twice a week, water regularly, aerate, fertilize, sometimes remove weeds

As a landowner, it is your moral duty to contribute to the preservation of the environment for future generations.

Can't it be a bit smaller? The immediate erection of the index finger is very German... If you invoke the moral duty in land ownership, it should above all lie in residential efficiency, in order to avoid sealed surfaces from the outset. The first duty would therefore be NOT to build a single-family house, but a multi-family house. Now remember your inheritance thread concerning your single-family house. Notice something? Hypocritical lectures don't make anyone rethink. I would like to pose the question as an impulse as to why one even has a garden plot if one doesn't want to do anything with it? A very large terrace, possibly a penthouse apartment, would have been the better choice then?

Wrong. See #24. I would actually be interested to know if your development plan says anything about it. Have you ever looked into it?

Yes, just checked again. It only says something about the plantings along the street and the noise protection walls. And otherwise that you’re not allowed to fully concretize / completely seal your property (floor area ratio). Although that would actually be just right for me ;) Just kidding, before someone gets upset again.

I grant everyone what they like. But bringing unnecessary plastic products into nature, that’s where the wagging finger is needed.

So, you’re really hitting your thread hard with your wrong assumptions – that’s okay: that’s what a forum is for, to inform.
But then it’s also up to you to read carefully:

You didn’t get hostility from me, but the information (among others) about the environmental outrage. It’s up to you to reflect on that.

I just understood your "I'm out" as you being absolutely displeased with what I want to have. But currently, 80 - 90% of gardens / outdoor areas in new housing developments look like that. That’s just what’s "modern" at the moment. Just like driving SUVs, which also isn’t necessarily the best for the environment. And I find your tips (also in other threads) quite sensible. You obviously seem to have a green thumb :)

Okay, then at the end of the day only lawn mowing remains. (Not even sowing)
Then you have to get a landscape gardener to come and create a plan. Warning! Costs money! Then request 2, 3, 4 offers and quotes.
2022 is certainly already too late for this topic. Implementation in spring 2023.

Is sowing really that complicated? 2023 would fit perfectly anyway, since the house probably won’t be finished until the end of this year / beginning of next year.

Uh, lawn as you plan it is pretty much the most maintenance-intensive thing there is.
At least mowing twice a week, regular watering, aerating, fertilizing, sometimes removing weeds.

I naively assumed the lawn of my parents. There it’s only mowed every 1-2 weeks (still conventionally without a robot) and scarified twice a year.

Is sowing really that laborious?

Can you breathe independently? If yes, then you have the appropriate qualification for sowing ;) . You rent a seeding aid for 5€ (so that it is sown evenly), lightly hoe everything once, and until the first mowing you only take care that it is watered properly. That's it.

This is not lawn. You have weeds, brown in summer and more like a meadow. You don’t want weeds.

Low-maintenance means natural. Coordinated plants that cope with the natural conditions, that fit the location. No bare soil. Skillfully designed, it improves the microclimate on the terrace. What you see 90% of the time in new housing developments is unimaginative, usually cheap looking, and creates problems.

What do you think is left of that expensive [Rollrasen] after a year without watering, without regular mowing? There are grass mixtures that can withstand drought, that don’t need mowing for weeks in summer, but weeds come and you have to reseed and water yourself.