Why don't construction prices go down?

Actually, it doesn't really matter anymore, because Germany no longer plays a significant role in some key technologies of the near future. These include batteries, AI, microchips, Big Data, etc.

This does not mean that the doors will close here in 5 years and the last person will turn off the lights. But times will become more difficult and there will soon be a lack of money for many social benefits. This includes [Bürgergeld], pensions, and maximum hospital care for everyone regardless of condition and age... Many things will have to be adjusted to international standards...

I stick to the example of the private individual. Yes, there are differences. But basically the mechanisms are the same.

Sorry no, I have to make it clear: Even the basic mechanism is not the same. Actually, nothing is the same. The state uses a different means of payment, namely central bank money. This is not a physically limited asset for a state - as long as it is its own currency. A private individual has demand deposit liabilities, which are always physically limited for them. Also, a private individual is expected to make real net repayments, as they die, in the literal sense. Even as a didactic simplification, the comparison simply does not work, as it obscures essential matters.

It doesn’t really matter anymore anyway, because Germany no longer plays a significant role in some decisive technologies of the near future.
To name a few: batteries, AI, microchips, big data, etc.

Don’t see everything so negatively. In AI research, Germany is still at the forefront – also number 1 in Europe. We also play a bit along with the big countries when it comes to data centers – among the top 3 in Europe. Frankfurt is one of the largest locations worldwide (power consumption over 800MW according to a study by Cushman Wakefield).
Chips have never been our strength, with batteries the ideas are there, but the implementation is missing.
But we have to continue to create the framework so that we don’t fall behind. That is the problem. You can forget a data center without cheap electricity. But the waste heat can be used directly for local heating networks.

But times are getting tougher and soon there will be no money left for many social amenities. This includes the citizen’s income, pensions, the maximum care in hospitals for everyone regardless of condition and age... Much will have to align down to international standards...

Full agreement. The “I lean back and enjoy all social amenities” time will (and must) be over.
But please don’t take the USA as an international benchmark.

Sorry no, I have to clarify: Even the fundamental mechanism is not the same. Actually, nothing is the same. The state uses a different means of payment, namely central bank money. This is, for a state—provided it is its own currency—not a physically limited good in any way.

But that doesn’t help if the money is worthless. You can print central bank money endlessly. Then it goes bankrupt, no matter what mechanism. Sovereign defaults are common—even the Austrians have gone through them twice. So much for investors who bought "safe" 100-year bonds.

Also, a private person is expected to make real net repayments, since they die, literally.

Leave aside the repayment; the private person slipping into bankruptcy hasn’t even reached that point. For states, it is the interest payments that always break their necks.

Sovereign defaults are common - even the Austrians have gone through them twice.

I feel like I’m being fooled. Hopefully a misunderstanding?

Austria was bankrupt in 1811, under a precious metals standard. But we are talking about the fiat currency world after the end of Bretton Woods.

The most recent case in Europe I recall is Russia in 1998, which, after a forced devaluation of the ruble exchange rate, could no longer service its debts - namely those in foreign currency. Argentina defaulted multiple times on dollar-denominated debt. And Grundriss on euro-denominated debt.

Please name a sovereign default due to debt in its own currency under the current monetary system.

The mechanism for states is exactly inverted. States can only take in what they have previously spent.