Building Insurance: Questions

Lower Saxony... nevertheless, I doubt the purpose of the extended elemental damage coverage in our area. Only heavy rain is noted there as a moderate risk. We don’t have a basement and build 20 cm above ground level. Moreover, damage of 1000 € first has to occur.

I know that I might make myself unpopular with this statement, but

Anyone who builds a house, which today costs roughly around 500,000 euros, should not save in the wrong place (on insurance). It is probably the investment of your life.

I know that I might make myself unpopular with this statement, but

Anyone who builds a house, which today costs around 500,000 euros, should not save on the wrong end (insurance). It is probably the investment of your life.

No, not at all for me. That’s the best argument I’ve read in this thread. House = life-time investment

... and yet the average damage in the Burgunderbratenkreis (no idea what exactly it is called) - which according to the website was the most affected district during the 2008 flood - was an average damage of 13 k€ and not 500 k€. But I will think it over again.

Again on the subject of the deductible of 300 €: "it is so low, definitely without deductible" I consider to be grossly wrong... especially in this example one can quite clearly say when the model is worthwhile and when not... namely exactly when one has damage exceeding 300 € less often than every 7 years.
Objection of gross negligence is clear and also taken into account.

... and yet the average damage in the Burgundy roast district (no idea what it is exactly called) - which according to the website was the most affected district during the 2008 flood - was affected with an average damage of 13,000 € and not 500,000 €. But I will think it over again.

Let me give you another consideration:
Until 2002, the damage incurred in the Elbe/Mulde region (Saxony/Saxony-Anhalt) was also negligible. 2002 was, to my knowledge, the first severe flood in more than 100 years in this region (or even longer). Accordingly, many had not expected anything like it at all.
If they did not by chance still have an old GDR insurance (which generally covered natural hazards) - contracts taken over by the Allianz - they were out of luck, since a new contract (with another company) was mostly concluded without natural hazard coverage on the grounds that "Nothing has happened there for over 100 years."

As I said - nothing happened for decades/centuries.

You are right... write it down on my To-Do list...