Special repayment, saving or consumption?

For us, it is a mix of everything.
Our financing consisted of 4 components. One of them we could repay monthly at will and over the last 5 years since moving in, we have regularly made special repayments. Sometimes just a few euros that were left in the account at the end of the month, sometimes larger amounts from bonuses or tax refunds. At the same time, we have also invested a lot of money into the house. Garden design, the occasional piece of furniture, lamps, curtains, basically everything that comes up over time.
At the beginning of the corona pandemic and the associated reduced working hours, we completely repaid this component from reserves in order to reduce the monthly expenses.
On another component, last month we made the maximum possible special repayment and thereby almost completely redeemed it. Half of the installment was still debited yesterday, so this part is now also done.

Now only the main loan and a KFW component remain.

Actually, the plan was to increase the monthly repayment on the main loan so that the monthly installment remains the same, but this component is paid off much faster now.
The corona crisis opened my eyes and showed that something can always come up, and a high repayment (we had a total of almost 1800 euros in installments) is possible but can also be dangerous in times of crisis. My industry is heavily affected and in our company, about 20-25% of jobs have been cut in the last few months.

For this reason, we are now conservatively saving the loan installments from components 3&4 in the overnight money account. At the end of 2021, we will decide what to do with the money, provided we have not needed it until then.
Currently, I favor a special repayment on the main loan (as the interest is still 3.7%), but maybe I will also just leave the money there to completely repay the KFW component in 2025 and avoid needing follow-up financing for it.

Of course, a little bit also flows into consumption. Less the 5000€ long-distance trip, but here and there a "toy".
In the end, it costs almost exactly as much at the end of the year.

We also built significantly smaller and significantly cheaper than many others, probably comparable to . Our total price at that time was about €300K including land, garage, and landscaping. At that time, our income was still well below 4k, so not many extras were possible. Meanwhile, the monthly income has increased by more than the installment and special repayment combined. Clearly, it then becomes much easier to simultaneously make many special repayments, invest in the house, and also invest in ETFs. However, at the time of building the house, this was not foreseeable in this form; otherwise, we might have installed more extras. The advantage of building cheaply is that we are expected to be done about 12 years after moving in.

A stupid question:

If I want to take out a loan of €550,000 and split this loan into several individual loans:

for example

1x €120,000 KFW 153 loan
1x €250,000 30-year fixed interest period
1x €180,000 10-year fixed interest period

The term for all loans (except KfW - which is already "contractually" fixed) is 35 years - repayment rate varies depending on the loan, but between 2-3%.

Assuming I receive a very large inheritance after 10 years - can I then fully repay the €180,000 loan after 10 years? In other words, is it possible to fully repay the loan after the fixed interest period ends? What I want to say/ask with this: Is the fixed interest period decisive for when I can fully repay the loan? Or does it not matter how long the fixed interest period is, since the term of the loan itself (until it is paid off to €0.00) is decisive?

We are considering whether a 30-year fixed interest period is necessary at all, since we also expect an inheritance within about 20 years and could therefore fully repay a loan.

What I have also read - which would again make a longer fixed interest period make sense:

"Even if you have taken out a construction financing loan with a 15- or 20-year fixed interest period, you can terminate your contract after ten years. And this without incurring a prepayment penalty (§ 489 para. 1 no. 2 Building Code)."

you can terminate your contract after ten years. And that without any prepayment penalty

You have a special right of termination after 10 years. From then on, you can exit at any time and repay your loan. This is independent of the fixed interest period.

Say: The fixed interest period of 10 years has absolutely nothing to do with the loan term or anything else - it only serves to limit the risk and either secure the current interest rate for a higher interest rate for a long time or vice versa.

For the cancellation period alone, it is totally irrelevant?

If I have a fixed interest period of 10 years, then after 10 years I just have to conclude a new contract with the current interest rate and can then also repay the loan without any problems after another 10 years?

If I have a fixed interest period of 30 years, I can basically repay the loan at any time WITHOUT a prepayment penalty as soon as the 10 years have passed, correct?

Yes

Addition to the last question:
More precisely, after 10 years you can terminate at any time with a notice period of half a year, thus at the earliest after 10.5 years. However, in the case of inheritance, for example after 13 years, you could also terminate there first with a notice period of half a year. All this without [VFE].