Bauhaus: 2 full floors + staggered floor (approx. 200 sqm) - optimization

Yes, Munich residents are self-confessed stair climbers. Here, there is even still a fourth floor, namely the basement attached. Building without a basement is almost a mortal sin, because the space for storage and technical equipment must not be "wasted" on the upper floors under any circumstances. It also makes sense when the price per square meter of land is over €2,500. For the OP, however, it is just "garden hobbyism".

All of that is true as well. Although the 2500 is already the lower limit! Absolute madness.

To keep stair climbing to a minimum, we are planning with an elevator!

But there is only a narrow single garage on the boundary, right?

The color pictures do not show any boundary construction, but there is a narrow space on the terrace side. Three floors may be justified where the plot is small, for example, terraced houses and semi-detached houses are often built with a setback. However, this is by no means necessary here.

In Munich, at least 3 houses with a recessed top floor would be built on the TE's property. There would be no space left for a garden.

For years now, a house with 2 full floors + a recessed top floor has been under construction here. It looks good, but the recessed top floor is very small and set back everywhere.

...exactly, nobody builds two stories at the CentralPark in New York either.

One question is whether it makes sense if necessary - it can, but here it is not necessary.

The other is whether the design is good - here it is not.

As already wrote. The setback story is usually recessed on (almost) all sides and takes up no more than an estimated 30% of the floor below. Here, only a corner (roof terrace) is cut out and an alibi strip that is not even a meter wide barely suggests the setback story. I believe that is why it looks so unharmonious. Especially the north view. Then there's the garage and the wrap-around window front. It doesn’t have a masonry corner pillar. That makes it look even more like a Tetris block.

The OP just has to reconsider their priorities. I wouldn’t voluntarily plan an additional story if it’s not necessary. After all the garden effort, hauling two stories up? No thanks.

...exactly, no one builds two-story buildings in Central Park in New York either.

But that would be a statement.