200K real estate purchase with 80% equity (unexpected inflow)

There is no entitlement to repayment WITHOUT prepayment penalty, you certainly meant that.

Let's make it complete and correct:
1. There is basically no entitlement to repayment within the fixed interest period!
2. First exception: special termination right according to §489 of the Building Code (10 years + 1/2 year after full receipt of the loan amount)
3. Second exception: sale of the property ==> then always according to the legally regulated calculation of the prepayment penalty
4. Third exception: contractual agreement
5. If the bank "just lets you" make a special repayment, it is completely free in calculating the prepayment penalty. You can accept the price or leave it.

5. If the bank "just lets you" make a special repayment, then it is completely free in the calculation of the prepayment penalty. You can accept the price or leave it.

There are often contractual agreements that you can make a special repayment of X% once a year without a prepayment penalty. Or does that always mean WITH a prepayment penalty? Of course, the details are in the contract. But what is common in this regard?

No, then they are without prepayment penalties. Instead, that is factored in with about a tenth or so more interest.

There are often contractual agreements that allow you to make a special repayment of X% once a year. Without a prepayment penalty. Or does this always mean WITH a prepayment penalty? Of course, the exact details are in the contract. But what is common in this regard?

See my point 4. Common ranges are between 5% and 10%. We also had (still have?) a full repayment option from year X on offer. But every option costs you something. That has to be clear. Always, even if you don’t see it.

Instead of €120,000, only €40,000 needs to be financed. Do you then have to go through the entire offer process again?

For €40k you will probably not get any real estate financing at all. They usually start at €50k.

For 40k€ you will probably not get any real estate financing at all. They usually start at 50k€.

And then the interest rates are much higher, since you only get a consumer loan?