Construction costs are currently skyrocketing

Interest rates will rise. Even the current interest rates are still historically low. The market has been practically flooded with money in recent years. This was (and is) a reason for the still immense demand for homeownership. Debt costs too little money.
The now relatively high inflation will also lead to higher interest rates: fewer people will be able to afford homeownership – so demand will decrease. Theoretically. However, there are dozens of other factors: supply, price developments in the construction sector, population development, key interest rate trends, alternative investments (resp. yields of these investments), and so on and so forth.
It certainly will not get easier...

I am of the opinion that none of those present here will ever again see interest rates below 1 percent in their lifetime. The low point of interest rates has been passed and will never return. Realistically, key interest rates should be at 6 percent and mortgage rates at 8 percent. Anything else contradicts all economic principles. Due to artificially kept low interest rates, we have seen bubbles in various asset classes and a phase of extreme indebtedness of states, companies, and private individuals. This has been accompanied by supply shortages and inflationary price developments. And I fear that the external constraints from a monetary policy perspective make drastic and rapid interest rate hikes unavoidable. Inflation, especially that of food prices and energy, will become a danger for the political class. The pressure on central banks to rein in inflation will increase significantly. We are currently seeing how the USA is trying to calm its voters. The USA has quietly and secretly increased its import of Russian oil by 40 percent, while Europe is pushing for an oil embargo. Likewise, under pressure from American farmers, the import ban on fertilizer from Russia has been lifted again. Yes, the Americans continue to get fertilizer from Russia while we no longer receive any. There it is about damage control. And with us, the damage is getting bigger.

Your argument is, to put it mildly, nonsense; furthermore, you fundamentally seem to have no idea what you are talking about. Nevertheless, the overall risk of a high financial single investment has increased and is more dependent than ever on the regional political course.

I don't want to believe it, but even -5% interest rates could become a reality!

You have no facts. And obviously no idea. When I read "regional political course," it horrifies me.... Have you experienced 8% interest? No? I have. The future will show. Anyone who thinks interest rates will stay low or even fall is just naive.