Possible funding amount / limit

If I compare us again... after all the saving, we live on 2500€ (- electricity, - phone, - water, - BAföG) per month and I would have no problem increasing that (meaning we live relatively frugally - where it makes sense) - what one sometimes forgets is the swimming course for just 100€ per child, the winter shoes for 50€ per pair, deposit for the class trip, the birthday brunch for 70€, the children's winter clothes for 50€ (from H&M), plants for the bed for 100€...

You were still missing 400€ - new cars would then be the new Opel Corsa from 2005 and the washing machine from Beko.

Why do you then pay off the BAföG in installments instead of paying off the remaining debt completely?

I know this and have a similar case (KFW student loan). In my case, for example, I am currently trying to be debt-free in all respects by the start of the construction phase. In my example, this exactly works out with the monthly repayments. Nevertheless, currently available equity is not used to pay off this loan at once (because, as mentioned by the OP, the loan is interest-free).

Whether the current loan will play a role in the upcoming interest negotiations (assuming one should be debt-free at the start of construction) I cannot say yet.

I would advise the OP to be debt-free during the construction phase; in my opinion, every euro that still has to be paid off alongside other things at that time is too much.

only 100 € savings on a BAföG loan doesn't make it "big" here...........

Because that makes sense - BAföG is interest-free.

At our time, there was a significant discount for paying off the BAföG debt in one lump sum. I would have to check the details. Even without a discount: 22,000 euros in a savings account at 0.x % and then 7,800 euros (BAföG) debt outstanding ... I would ensure clear conditions.

(Savings account is an assumption, maybe the equity capital is more or less fixed, then it looks different.)

That depends... If you received a lot of BAföG, sometimes even the discount won't bring you below the maximum limit of 10K €. Liquidity is not free either - if the 10K € additional equity, for example, saves you 0.1% in interest, you really have to do the math... Even with a 2K € discount through direct repayment of the BAföG.

Besides the arguments from , the deadline for choosing a one-time payment with discount or installment payment will have already passed.