Floor plan tube house L-shape triangular plot including oak tree

Well, the line runs across the entire property.

Could it be any more stupid?
I would get myself a bit of weed in Holland for your tree to calm your nerves.

Well, the line runs across the entire property.
The excavator (even with diesel) can't work there, too dangerous.

What kind of nonsense is that? Is it a regular cable for households? Or 10,000 volts or more? He can clearly see where the cable runs.
How do they work when they backfill the cable? Surely not by hand.
With us, cables are even repaired under voltage. Protective equipment, and off they go.
Which federal state, if I may ask?

35 kV

NRW

Ah. Then I said nothing. But regarding refunds or similar. You surely have some ongoing costs like construction power distributors, scaffolding, or similar. If it really should be illegal, then I would write a nicely worded email to the [Stadtwerke] and ask if you could somehow come to an agreement. (Seriously meant nicely) You don’t need a lawyer or anything for that. Actually, they are fairly lenient when it comes to stuff like that... At least here in Hamburg

How many euros could be generally estimated per week of construction downtime?

You will not achieve anything by being vague; you must specifically list and prove where you incur costs due to the delay so that it can stand up legally if necessary.