Daily savings accounts - How should one save best?

if corresponding storage space is available, invest money in building materials

But with building society savings contracts, one shouldn’t overdo it; these often incur fees, you need an allocation, and often complete annuity loans are more sensible afterwards (building society savers have high repayment rates -> high monthly burden). The savings-building society contracts can possibly be useful, we still have a very old one running for which we get 4.6% interest, unfortunately it will soon be so full due to the interest that the bank is allowed to dissolve it. But until then, we'll leave it as is :P

Especially building society savings contracts make sense with the currently low interest rates to secure exactly these for the period after the initial fixed interest rate term, or do you know what the interest rate level will be in 10 or 15 years? They are not suitable for pure saving precisely because of the interest rates ... but as a component ideal. And honestly, I gladly pay a 1% closing fee if I know that in 10 years I will only pay 2.45% interest! There are definitely more expensive products.

This is purely a speculative object, it was about saving! If you now take out a building savings contract over 100k, into which you have to pay in about 40k, then it is already a matter of luck to get the allocation on time if you do not fill it up quickly enough. If it is missing and you need an expensive interim financing, you have already lost money.
If the interest rates are lower in 10 years, you have lost twice: little savings interest and the 1k closing fee gone, PLUS additional fees.
And you generally have to consider the fees, mostly it is a bad deal.

Therefore, I advised checking the existing! and already saved building savings contract and using it as a building block! Sorry, but that interest rates will fall even further in the long term... I wouldn't count on that!

I have been reading the argument about interest rates every year for many years (certainly 10?). But even if they do not fall, or only rise slightly, with the Bausparer you "lose out"; because you rarely get the current best interest rate and additionally there are fees! Existing Bauspar contracts should indeed be reviewed, but honestly, and possibly better to dissolve them and invest the money. You should not keep/use them at all costs. As a component in financing, I would like to point out again the high fixed repayment rate, which then reduces the total amount to be borrowed, since for other loans the remaining monthly repayment amount is relatively small. I say from personal experience that you have to be careful with it, even though I have a good savings Bauspar contract, I have "fallen flat on my face" with another one. The arguments for it were exactly yours, Souly, but in the end I definitely threw away 3-4k euros with it. In most financings here in the forum, a compact annuity loan "wins" most often; with the accumulated equity capital you often get interest rates that undercut all others, with high security (long term).