Is it possible to withdraw cash from the construction account?

Luckily, my Sparkasse neither requires pictures nor invoices. All disbursements are carried out relatively uncomplicated. They only said that they might send someone over after completion.

Crazy o_O
I don’t find that all that desirable. Don’t banks actually have an obligation to check such things?
Whenever I watch those YouTube documentaries (and also trash TV) about building, I always wonder how homeowners manage it. To be stuck with a botched shell construction but already having paid about 95% of the agreed sum to the company. The company usually goes bankrupt shortly afterward and pulls the same trick under a new name with the next victims, while the mailbox at the old company continues to overflow with letters from courts.
Whenever I see/read something like that, I think, "My bank wouldn’t put up with that." I actually find that good and right. That’s not harassment of the customer, it is also there to protect us.

Well - it significantly reduces the "administrative" effort in an already stressful construction phase - besides, you can sometimes slip the craftsman next door something under the table (that's often how it is in practice). If the result is right and both the client and the bank are satisfied with the outcome, that's already great and provides flexibility.

I know it like that from the [Sparkasse] as well. They are super relaxed about it.

We are also with the Sparkasse. They only make partial payments to the general contractor over 25k€. For everything below that, I have to fill out a form stating that I want 25k€ (minimum amount) transferred to the repayment account (our family account). From that, I pay whatever I want. No checks. Recently, that was the first partial payment to the general contractor of over 1% for the planning discussion. From that money, I pay for example hardware store purchases or purchases on eBay classifieds. I am not supposed to collect receipts. When the amount is used up, further financing would have to be done.

Fortunately, my Sparkasse neither requires pictures nor invoices. All withdrawals go through relatively uncomplicated. They only said they might send someone over after completion.

It was exactly the same with us. Always a short email with the request for a withdrawal amounting to XY euros, and one day later the money was in the construction account. Proof was never required.
Therefore, cash withdrawals for, for example, hardware store purchases were completely unproblematic.

But it seems to vary greatly from bank to bank. Just ask your bank.

As a rule, banks want proof that the money is actually being used for the construction and not for the new Lambo. The Sparkasse paid me 8000€ remaining from a partial loan to the reference account upon an informal request without any proof. Normally, they want to see the invoice for the partial payment and then the transfer is made. Whether this is really checked precisely is another question. In case of doubt, just call the bank and ask how they handle it. You don't want them to suddenly want to see invoices and the scaffolding from the classifieds causes trouble.

We are also with the Sparkasse. They only make advance payments to the general contractor over 25k€. For everything below that, I have to fill out a form stating that I want 25k€ (minimum amount) transferred to the repayment account (our family account). From that, I pay whatever I want. No verification. The last time was the first advance for the general contractor over 1% for the planning consultation. From that money, I pay, for example, the hardware store or purchases on eBay classifieds. I am not supposed to collect receipts. When the amount is used up, one would just have to refinance.

True, I was also asked not to request less than 25k. The bank might be relaxed with me perhaps also because my loan is only at 100k.