Best possible preparation for the initial interview

It is not a job interview, nor does the financer or advisor care about your nose, attitude, or clothes. What counts is the current situation and facts. You need to consider possible scenarios with/without children, parental leave, unemployment, etc. yourselves.

Which documents should we compile and how else can we prepare to go into the first financing meeting in an exemplary manner?

What do you expect from the bank meeting? Prepare your questions.

If you live in reasonably solid conditions, the offered amount is far too high. How much you want to take on is something you have to decide yourself.

Very valuable advice! Also the pointers that in the end you have to decide yourselves what you can and want to actually take on and how you assess certain risks. The bank just gives you money; they don’t provide "life counseling." Think beforehand about what you can and want to handle. For the bank/intermediaries, you only need your current numbers; they don’t want to know more and don’t need more. The conversation is quite relaxed. You’re not presenting yourself as if for a job. Rather, you’re looking for a business partner, so to speak.