Which installment should be paid off first?

The "problem" can be solved by different terms, which the OP has. After 10, 15, or 20 years, you simply take the accumulated equity and finance less afterwards

Also possible. But I find it better to repay immediately instead of accumulating money for 5 years. Unless the credit interest rates rise above the loan interest rates. In that case, I would also stop the special repayments.

or adjust the repayment of the remaining loan upwards.

Provided the repayment rate change is agreed upon.

The situation only arises if the salary increases more than planned/expected.

When the loans mature after 10, 15, or 20 years, I refinance completely freely, so I can then also redefine the repayment.

Best regards Drik Grafe

You are right that the problem only occurs with salary increases. However, the TE, regarding the component 2 with planned special repayments of 4000-5000€, would have already quickly exhausted the maximum special repayment of probably 5% with 200€ more net per month and the elimination of the installment from the 3rd component. That is not unrealistic in 10 years.

But I just read through the conditions of the new 153 KFW loan. It can be repaid early at any time. Even if you exhaust the option with the 2nd component, you could still make special repayments on the KFW component. So all is good.

But I just read through the conditions of the new 153 KFW loan. It is freely repayable early.

However - it can't be the KfW 153!?

With a 10-year fixed interest period, the interest rate for the 153 is 0.75 and not 1.16%.
The 1.16% fits more with the KfW 124 (early repayment here only in a lump sum).
However, the repayment does not match here (according to the KfW calculator).
With a 10-year fixed interest period and 25 years term and one year repayment-free, we are at 3.62% repayment.
With a 10-year fixed interest period and 20 years term and one year repayment-free, we are at 4.71% repayment.

I rather suspect that the OP has a similar bank loan in prospect with the 2% repayment, where the option for early repayment is included.

What also comes to mind here: Often only early repayment options of 5% of the loan amount are granted. With this, the OP could only repay 2,500 euros on this loan (although it is of course not excluded that 10% were also agreed).

Whereas - it can't be the KfW 153!?

With 10 years fixed interest, the interest rate for the 153 is 0.75 and not 1.16%.
The 1.16% fits more with the KfW 124 (special repayment here only in total sum).
However, the repayment does not fit here (according to the KfW calculator).

The KFW 153 is also the first building block with 100,000€ and 1.51% interest with a 20-year fixed interest period.

Ah - every time I forget that the amount for the KfW153 has doubled in recent years. I had focused so much on "highest interest rate" vs. 50,000 that I hadn't even looked at the other one.