Is construction financing possible? Please provide assessments.

I do not want to deny any of that, it was not directed at the OP, rather to be understood as an impulse. I don't like it either, but that is the way it is with the credit system.

The problem is that such impulses often reach the wrong people, namely those who desperately try to keep up and get into the market quickly before it finally moves out of their financial reach. A good read on the subject is "Irrational Exuberance" by Robert Shiller. There is also the aspect of asset consideration. Owning a home is a bad investment because everything is concentrated in one big lump. Living rent-free is nice but not the same as cost-free, and the lump can only be turned into cash if you sell your own house and move. For banks, by the way, this is also not entirely risk-free; I only recall the financial crisis that put banks in danger one after another in America. This is naturally favored by the fact that in the USA it is much easier to get rid of credit and residual debt than here in Germany. But when such loans default en masse, e.g. due to unemployment, banks will also have trouble collecting their money.

I personally consider the risk that interest rates will rise again to 5 - 6 % very unlikely. However, they don't even have to rise that high to put many financings in jeopardy. In my view, it is enough if 3 % become due for the follow-up financing.

Independent of the financing, one should also keep an eye on the maintenance and repair costs that will be required over time. Who says that the heating systems installed today will still be approved in 20 years and that one won't have to buy a new heating system due to legislation?

In our town, I now see many houses from the 80s to the early 2000s that look completely rundown because the owners cannot renovate anything. In the older houses, the owners are mostly retirees and may no longer notice the damage. But with the houses from the 2000s, it really breaks my heart. People around 50 +/- live there, and the whole house is totally neglected and has a backlog of investment...

The other day there was an article in the newspaper titled "10 ways a home can make you unhappy." I honestly found it very interesting.

Furthermore, for about a year now, more and more properties in our area have been going into foreclosure because the buyers have grossly miscalculated the costs and at the same time overestimated their own effort. But something like that never happens to you yourself. That only ever happens to others.

The comparison to America is flawed in that it was not (only) about risky loans, but that these were collected as beautified investment packages and then resold/bought without rechecking how valuable they really were. That is what truly drove Lehman & Co. into ruin. Today, however, there are several security instruments.

I don't want to deny any of that, it was also not directed at the OP, rather meant as a stimulus. I don't think it's good either, but that's how things are with the credit system.

Of course, you can push the credit to the absolute limit, and in isolated cases, that is certainly okay. However, a basic prerequisite for this is that everything is very well planned. An existing property in the big city can be quickly sold in an emergency. The risk is low, despite the extremely poor ratio between purchase price and income. Even a 2% repayment will eventually become acceptable there. Let me say this very clearly, please don't take it personally: Here there is an (oversized) craftsman’s dream with little planning and above all unknown costs that fluctuate in the six-figure range. Following the motto "Couldn't I just spontaneously take out 100,000€ more credit?" That is pure risk.