Construction financing - colorful mix with building savings contracts?

Hello everyone,

we would be interested in your opinion. We would like to finance a single-family house and have the following key data:

Property value: 415,000 EUR

Equity capital: 145,000 EUR
Debt capital: 270,000 EUR (loan requirement)

Equity ratio: 34.9 %

Household net income: 3,900 EUR (2,500 EUR + 1,400 EUR)
- two adults, 1 child (possibly another child planned)

To manage the 270,000 EUR, the bank has made us a financing offer, which consists of the following components:

1. Building savings contract (150,000, interest-only loan)
2. Building savings contract + Wohnriester (50,000, interest-only loan)
3. Annuity loan (70,000, annuity loan)

Monthly we would have to pay around 1,180 EUR for the loan. The total effective interest rate with Riester subsidy is 0.94%. In total, we pay the bank around 305,000 EUR, which is why the loan costs us 35,000 EUR (= 305,000 EUR - 270,000 EUR).

That the bank offers us building savings contracts instead of "normal" annuity loans with a long term has surprised us. Are such constructions common? What pitfalls are associated with them?

Independently of the above offer, do you think we can basically manage the loan (especially if a second child comes and the second income is lost)?

We would be happy if you could share your opinion. Thank you very much!

Deferred taxation for Riester was discussed? I'm not a fan of that kind of thing, everything would have to be calculated in Excel. Have you ever asked Interhyp and co for a counteroffer? Are 1-3 all full amortizers?

And is the repayment of the building loan contracts that will be due at some point, which will replace the interest-only loans, also included?

I would definitely prefer a clear annuity loan there as well. Possibly with [Kfw] or is that not an option?