Is a pedestrian crossing necessary if there is no sidewalk (in Berlin)?

It is even a law, the quoted part is the first paragraph. The law has existed since 1999, as far as I could find out the first paragraph in this wording applied until the latest version from 2021. How do you find out which regulation was relevant before that? There is nothing about that in the introduction of the law, and a simple Google search also could not find anything conclusive.

Yes, I think so too, waking sleeping dogs is the worse option, but according to the entrepreneur's statement, it will happen sooner or later and then there would be a risk that you have to pay additional fines because you have unlawfully driven over the "not intended for driving part of the road" all the time. He also said that the corresponding office has filled 7 new positions and he now has one customer after another for whom he has to establish the crossings. But that could all also be just sales talk. We will talk to another entrepreneur tomorrow, let’s see what he says about it....

Which brings me to the next question:

Does anyone have experience with compensation payment/replacement planting of a tree on public ground? I find a lot about protected trees on private ground, but is it then simply the same plus processing fee or does it become more expensive again if it is a public tree?

I would say a path can also be paved with gravel, so it is an inexpensive solution that lets the tree be a tree...

Yes, that may be the case, that would at least explain why the neighbors often only have such drives. However, with us, it's not even gravelled. It is simply compacted sandy soil, probably mixed with humic components. There was no driveway there before. That means, in case of doubt, we would have to create one (no matter how) and then a substructure must be installed, which is already in the root area of the tree. I almost fear we can't avoid it.

The question would be, just wait and save in the meantime or rather do it right away?

It is even a law, the quoted part is the first paragraph. The law has existed since 1999, as far as I could find out the first paragraph in that wording applied until the latest version from 2021.

Standards have to be definite. So there must be a definition of "non-passable road components," "crossings," and "paved." And if nothing to the contrary is stated, a surface bound with water-bound aggregate is also considered "paved."

Yes, that may well be the case, but a water-bound gravel surface will also require a frost-proof substructure and appropriate material (precisely not humus soil) and must be compacted at least once. However, all of this will involve interventions in the tree’s root zone and is therefore subject to separate approval, unless they even completely deny us this because it is new construction and we wouldn’t have had to plan the access there.

I notice once again that we were poorly advised by our real estate agent and general contractor.

To be honest, if it doesn't bother you yourself, just throw a few centimeters of gravel on top without a substructure. I doubt that there is a precise work instruction for that, let alone that someone checks and goes digging with a shovel. If you say others have done it the same way, even more so.