Building as a single, marriage, and prenuptial agreement

But everything else, and especially the understandable attempt to secure one's own life achievements so far in front of the partner

Then you simply don’t get married. Purpose served, without any contract. No compensation of pension points if one has only worked part-time because of the children, no compensation for assets acquired during the relationship (and certainly not for those already existing before). She does the shopping and then, if necessary, takes the contents of the fridge with her and he pays off his property.

This is expressly not directed at the OP, who is precisely looking for a fair solution.

Otherwise, I find in the case described, at the latest when children are involved, a "normal" community of accrued gains not a bad thing. If she supports him, so he can maintain his usual income — then she can also benefit from the increase in assets that arose during the relationship in case of need. I think it’s a good thing to document the asset status at marriage (=> content of the prenuptial agreement), then you have that if it is ever needed. And from then on, you manage finances jointly.

I always find such discussions very interesting because I simply cannot understand this discussion about the fairness regulation regarding money.

From day 1, we put everything together (over 10 years ago, poor studies) and have never had a discussion about my and your wealth.

It's not an art either, when both start together at 0.

I always find such discussions very interesting because I simply cannot understand this discussion about fairness rules regarding money.

I also find the discussions very interesting. Sometimes it shows what priority money is given, sometimes how little trust people have in themselves, and sometimes how high some people's need for security is. Understanding this from outside one's own situation is the interesting part, because where else can one learn if not outside of one's own thought patterns.

It’s not really an achievement when both start at zero together.

I see it similarly. The likelihood is high that it will be viewed differently in other situations. He might bring 100k into the marriage, she nothing. She takes care of the future children, he goes to work and earns good money. She gets bored, starts an affair, and leaves the husband. Well, and then everything was pooled together from day one. And she wants to be paid out. As a husband, you’d surely find that great. How is anything calculated? What is the trust from the beginning of the relationship worth? And on top of that come all the emotions and interference from outside. The roles are just exemplary and can be switched arbitrarily. However, this is not an unrealistic scenario. It’s worth thinking about at the beginning.