Special repayment, saving or consumption?

I can understand both variants equally well, but I personally now prefer the direct reduction of debt. Mathematically, looking back, that might eventually have been less sensible, but I like the clarity and rather the bird in the hand.....because with the other variants, I've already lost quite a few pigeons. I also kept an eye on prices/the stock market, and that made me rather uneasy. However, the reason for building my house is precisely to achieve a certain kind of peace, a feeling that cannot be calculated for me. It is probably also a question of one's own life situation or philosophy.

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Then let's strongly hope for you that you can also easily withdraw your ETFs after 10 years, without a crash or the like.

You can decide for yourself whether or not. That’s what the long fixed interest period is for, and then you can make a special repayment after 10 years or even only after 14 years.

The longer the investment period, the higher the return. If a stock market crash (or e.g. Corona) occurs, of course you have to be able to sit it out for a few more years first.

Even with a stock market crash, you will have already had significantly higher returns beforehand. The average return already includes stock market crashes. Assuming an investment period > 10 years (see e.g. return triangle), the stock market crash is therefore irrelevant. Of course, it is much more pleasant to have 14% per year instead of 2%.

You never have the option to quickly say: "I'll just have it paid out" – it’s just associated with a lot of risk.

Yes, you always have that option. With an investment period under 10 years, of course with a certain risk of loss. For investment periods > 10 years, the risk is manageable.
Sometimes a loan simply doesn’t expire spontaneously. You can gradually restructure that beforehand with a withdrawal plan.
More spontaneous for me would be cases like (long unemployment benefits/long illness/disability/accident). How do you get money in these emergency situations if it’s tied up in special repayments?

Also, you only have a certain % amount of special repayments per year. I can’t say I’ll have my 10k paid out and make a special repayment all at once... That way I lose valuable years, causing me not to be able to make my desired early repayment on my loan.

That is of course an argument for the first 10 years. But after 10 years you always have the choice and can calculate whether it makes sense to partially refinance and pay off the rest with the sold portfolio value, or simply partially or fully repay the loan, or let it run and only terminate later.

As I said, I take the middle way and also use the special repayments for our main loan. But I also like to keep financial reserves on hand to be flexible in emergencies and not dependent on the bank.
In such situations, usually everything comes together anyway. You might quarrel with the insurance because they don’t want to pay.
The bank gets nervous because an income disappears. There is no new loan under the new conditions anyway. Etc.

We will consume something right at the beginning because we want to make it nice for ourselves initially. So we will invest a bit in furnishing, but not too much. The rest will go into special repayments. Starting next year, we actually won't need that much anymore; from then on, I definitely think we will invest in special repayments. Maybe a small part in ETFs, but my gut feeling is that investing in ETFs is much less secure than repaying the loan. That's why we will put a manageable monthly amount into ETFs (more for retirement), set aside a solid monthly saving amount for house maintenance and "if something happens," but that will go into a daily allowance account or something similar, even if it loses value - so that we can definitely fall back on a good sum if something unforeseen happens, and will invest the remaining leftover money towards special repayments at the end of the year.

I feel the same way as Pagoni, I would rather pay off the loan faster because it's simply better for the soul.

We will already consume a little at the very beginning because we want to make it nice for ourselves initially. So invest a little in furnishings, but not too much. The rest flows into special repayments. From next year on, we actually won't need that much anymore; from then on, I think we will definitely invest in special repayments. Maybe still a small part in ETFs, but from my gut feeling, investing in ETFs is much less secure than loan repayment. That's why we invest a manageable monthly amount in ETFs (more for retirement), put aside a solid monthly savings amount for house maintenance and "in case something happens," but then in a savings account or something similar, even if it loses value – so that we can definitely fall back on a good sum if something unexpected happens, and will put any remaining money at the end of the year into special repayments.

I'm like Pagoni here; I would rather pay off the loan faster because it's simply better for the soul.

We do it exactly the same way

With the first house, we had 2 holidays, when the finances overtook the outstanding balance, and the payment of the last installment, both are good for the soul and inner satisfaction, so I am fully with