Construction contract - Uncertainty regarding payment schedule

This payment schedule is neither fair nor aligned with the mandatory contents of the consumer construction contract (valid from 01.01.18).

Apparently, a provider did not do their homework.

Then please clarify for the OP and also for us what has changed since 1.1.18.

He is probably referring to the fact that advance payments may only amount to 90% of the agreed total remuneration. That means the final installment may not be only 5% but must be at least 10%.

Then clarify for the OP and also for us what has changed since 1.1.18.

Why? That belongs to the responsibilities of those who run this forum or your lawyer. I have no time to explain all the many expansions and changes in detail.

The following passage is still in the contract but in a section dealing with costs that are not included (connection costs, etc.):

The contractor may issue interim invoices to the extent that they do not exceed 90% of the proven costs. At the same time, this also provides the security amounting to 5% of the costs in favor of the contractor. The remaining 10% is to be paid after completion.

My plan is to change the first installment to 1% and pay 10% only after acceptance. Then it fits, right?

That you do not understand this: if you change the payment schedule to your advantage without consulting your BU, what will he do? How will he understand it? He will say: Aha, that's the kind of person he is. There are already problems with him. Surely a teacher or otherwise too clever. So, I’ll show him who’s boss... and he simply won’t continue working. Bang. That’s how it is. Because he certainly has enough other contracts to avoid being annoyed by you. Karsten

I have not signed the contract yet. The contract is to be mutually amended accordingly. That's what I have meant all along.