Problem with the electrician - what would you do?

It's really crap to have such disputes. Basically, the electrician has to calculate his time and include it in the offer. If he miscalculates, that's only your problem if it arises from constant changes or extremely high communication needs. I would proceed as follows:

[*]Determine what is missing. [*]Withhold the amount for it + risk surcharge [*]Have it completed [*]Material price increases and pipe meters are not clearly identifiable to me, but also not so relevant in total. [*]Settle the invoice as last requested - with 100% functionality. [*]oh yes - and even if it's tempting: no remarks on the individual interpretation of the spelling - it just adds fuel to the fire.

That way you get the desired result and have the shortest time of trouble. Maybe not financially optimized by all rules of the art, but optimized for quality of life.

He is no good for it, he can't do it I had already paid... 50 rolls just for the screed? It felt like for the screed for the ground floor, upper floor, and attic = I would maybe estimate 1800m

Is the itemized list exclusively for the material because labor hours are summed up at the end?!

Just one point:
approximately according to the invoice 250 outlets in the form of sockets, motion detectors, etc. with a total of about 6 km of empty conduit, means roughly 24 m of empty conduit used per outlet assuming each location was approached individually, which is not reasonable and at the latest with double sockets questionable whether a 5x1.5 cable was pulled instead. You have an item of around 10.5k (net?) listed just for empty conduits there.

In the photo of the first offer, only material costs are shown, with one roll each for the cables as it appears. The cables (NYM) do not appear at all in the final invoice; I assume they are included in the flat rate for the sockets.

The individual items on the invoice for sockets etc. then (including cables and installation) do not seem so far off in terms of amounts, whether the quantities are correct, I would at least count them as with the roller shutters, the empty or protective conduits seem quite questionable from a distance.

Is the list of individual items exclusively about the material because at the end there are still labor hours

I didn’t understand that either, I think he simply is not allowed to do it and listed it separately.

Some cold air is coming in at the outdoor sockets, he did not use airtight boxes.

How much is the total bill now, how much money has been paid, and what remaining work is still outstanding?

What is the total bill now, how much money has been paid, and what work is still outstanding?

27,000 euros have been paid

What is still outstanding?

- actuators in the distribution board
- installation of fiber optics and presence detectors
- programming of KNX: for lights, blinds, window contacts, etc.

Again, at the beginning, are there cables everywhere and are they properly laid and labeled, and are all KNX components present? Are the actuators wired in the control cabinet? Do you possibly have a picture of how the situation looks?