Construction costs are currently skyrocketing

I can only think of one solution. Look for a (Polish) all-rounder nationwide. Still probably difficult for solar thermal, but maybe someone could cover the rest.
Rent a caravan, put it on the property, and let them work hard for four weeks...

That's exactly the idea we had too. Hire a Polish or Romanian crew, pay half the German price, and be happy. But I think we might still prefer to do it ourselves. And we can probably forget about solar thermal for this year. Mind you, I have been working on the heating issue for 11 months already. We have two other renovators in the area with exactly the same problems. So at least it's not just us. You start to doubt...

Unfortunately, German driving license law has also developed into a true bureaucratic monster. There are currently almost 40 driving license classes in the most senseless gradations. Even some police officers are no longer able to keep track of it.

How absurd this driving license law is is shown by the following incident. For example, a 16-year-old is allowed to get the tractor license L. Thus, he is allowed to drive a 40-ton trailer combination with a total length of 18.50 m and 500 hp on public roads.

However, with a speed limit of 40 km/h. From the age of 18, the young man may drive at 60 km/h with the driving license class T.

However, he is not allowed to drive a car. Not even an unbraked trailer up to 750 kg. But he could drive to school with a 500 hp tractor without accompaniment and already at 16. And although he is easily allowed to tow a 12 m long 25-ton trailer with the tractor, he still has to get the car trailer license at 18.

Regarding the costs, whether for tractor, truck or bus license, it is no wonder in the transport industry or agriculture that there are no more professional drivers.

Hardly anyone wants to put up with this anymore.

Unfortunately, German driving license law has also developed into a true bureaucratic monster.

I am currently demolishing a house and rebuilding it. The development plan requires archaeological supervision. Neither the archaeologist nor the office sees it as useful – but it’s stipulated, so it has to be done, costing 500-1000 euros.

Conversion of an attic: regulations require a fire escape on the house.

Fire protection requirements: demonstration in the local school auditorium – by now, 6(!) personnel plus a fire truck have to be employed.

Digital electricity meters: it should all be totally secure – end of the story: the meters come in sealed boxes and may only be installed under the four-eyes principle, including documentation on thousands of levels. Endless costs.

GDPR: ... no words.

In summary: In principle, good ideas are inflated until the core idea is completely brought to absurdity. This costs time and money – and in the worst case, an entire swamp of profiteers forms who keep putting their hands out for some certificates.

I can reassure you: I've since bought him one. But to be honest, he wasn't happy about it because he misses his old one.

Stupid question: Why am I obliged to replace his broken stuff?

Not obliged. It would be a concern of mine to help my father as far as I can if he gets into an emergency. Both financially and in terms of time. After all, he has done all sorts of things for me in his life.

We had exactly the same idea. Hire a Polish or Romanian team, pay half the German price and be happy.

And why don't you do it then? Have you ever advertised on that portal with the hammer?

But he could drive to school with a 500 hp tractor without accompaniment and already at 16.

No, he cannot drive to school. Class T is purpose-bound, meaning it may only be used for forestry or agricultural purposes. That means no "everyday trips." Class L was without purpose binding, but it no longer exists.