Financial plan with a building savings contract or with risk?

That is the problem, hard to understand.

I have corrected my description again.
Yes, I pay interest and into the [Bausparvertrag], there is 0.5% interest on the balance.

The [Bausparvertrag] is comparable to a 25-year loan. It secures the interest rate over a long period.
With the [Bausparvertrag] I have an effective interest rate of 3.85%, and with a bank loan I don’t know anyone who would offer you a 25-year term loan with these interest rates?
In years 11-15 the interest rates have not yet been determined. The advantage I have is that I can pay in arbitrarily more in years 1-10 and thus shorten the term until allocation. This reduces the uncertainty of the interest rates. After the allocation I have fixed interest rates again.
I will look at the matter again over the weekend.

The advantage I have is that I can pay in arbitrarily more during years 1-10 and thus shorten the term until allocation. This reduces the uncertainty of the interest rates. After allocation, I have fixed interest rates again.

The best would of course be if you have the contract ready for allocation in 10 years so that you don’t have an uncertain transition period..

This is the biggest problem here, since you haven’t paid anything off in the 10 years.. the interest rate increase hits you with full force because all €67,000 are still on the clock...

If you contribute €225 instead of €150 to the contract, it should already be "mature" after 10 years... this shortens the total term to 20 years and the interest costs to ~€28,000.

However, if you get a bank loan over 20 years with an interest rate of <=3.7% and use the €225 to repay it, that would be better/cheaper for you...

I have not yet found a bank that fixes their interest rates for 20 years or longer, or in a way that would be better than the building savings contract, that is simply the interest advantage of the building savings contract over time. Annually, I can make 10% = €6700 in special payments without paying a fee for it, so I can also speed up the process this way.

So far, I have not found any bank that offers fixed interest rates for 20 years or longer, or in a way that would be better than a home savings contract; that is simply the interest advantage of the home savings contract over time.

a "hoped for" interest advantage! It is not certain that interest rates will be significantly higher in 10/15 years than they are now... if interest rates remain at this level, it would be a clear loss.... a home savings contract is, in this case, a bet on rising interest rates... depending on the contract and bank loan, there is somewhere a break-even point...

How much do you want or can you pay monthly at most?

Why it is so difficult to find a bank is clear. They want to pitch you a home savings contract.

I had the case with the Sparkasse here: 10 years was a relatively good offer. 15 years was already out of the question. At 20 years, my advisor there threw in the towel and assured me credibly that they don’t do that, and if they do, it will be very expensive... So his model included 2 home savings contracts.

I didn’t want that, and went to an independent advisor. Inquiry at the same bank: immediately came with a 20-year offer, at conditions that were just like the 10-year offer directly from the bank to me.

Result: I looked for another bank with similar conditions (0.01% worse than my Sparkasse, then closed my accounts at the main bank)

We are currently also financing through a mix of KFW / bank loans and [Bausparvertrag].

We chose the [Bausparvertrag] mainly because you can use the lead time if the employer pays it.
For us, this directly amounts to €80 per month.