Light courts - Are they meaningful?, possibilities, costs, examples, distance...

That must be a window you can climb out of (with a ladder?), right?

Our state building code states that windows must be at least 0.90 x 1.20 m in clear opening and must be installed no higher than 1.20 m above the finished floor level; in the light well there must be a possibility to climb up (logically, the cover/grate must also be easily removable). But you should best check the state building code relevant for you to see what is required there. I can't say anything about the costs for a continuous skylight/light flooder; we decided on a light well. The window has the required 3 m distance to the boundary in our case.

And finally: How much space does a light well need? Is, for example, 4m to the neighbor enough if the basement is not elevated, so completely underground?

Are you allowed to build light wells right up to the boundary? And would it bother you if you can no longer walk past properly at that spot? If we assume a depth of 2m, then 4m length shouldn’t be too steep. And what is on the neighbor’s property after those 4m? If the garage is there, then it will be quite dark down there.

If the garage is there, then it will be quite dark at the bottom right

Oh, that's of course important to consider. There will be a driveway and then after 3 meters the house. Difficult with the light when you have houses on the left and right and need the area for the terrace on the garden side...