Costs, auditor's report

Good day,
this concerns the construction of a two-family house in Hessen. The structural engineer I commissioned sent me an invoice for monitoring / inspections of construction phases 1 - 4 amounting to 1,200 euros net. I had commissioned him for this amount at the time.
The invoice was accompanied only by a certificate according to Paragraph 83 Section 2 HBO confirming compliance with construction execution. Neither a report nor photos were attached, i.e., I have no proof that he actually carried out the work. On site, I only saw the engineer during the acceptance of the last construction phase because I wanted him to take a look at some cracks and therefore an appointment was made.
The structural engineer is also the one who prepared the structural calculations for the general contractor.
Is it common not to include any proof for the services invoiced?
Best regards

The verification engineer and the structural engineer may never be the same person.

In my opinion, this is a rip-off.

This is obviously a joke. The verification engineer is called because of a defect and then it turns out to be the structural engineer from the main contractor.

He has provided his proof through the issued confirmation. What did you agree on in the contract? Was he supposed to report regularly or monitor and confirm that everything went as planned? Tick it off - it is confirmed that it was built as planned. Should be fulfilled by the structural engineer.

He has provided his proof through the issued confirmation. What did you agree on in the contract? Was he supposed to report regularly or monitor and confirm that everything went as planned? Just check it off - it is confirmed that the construction was done as planned. Should be fulfilled by the structural engineer.

I basically agree with you. But that is not the idea of a testing structural engineer to check themselves. How can he confirm that it was built as planned if he was never on the construction site?

But that is not the idea of a structural engineer to check themselves.

That is certainly true.

How can he confirm that it was built as planned if he was never on the construction site?

Nobody knows how he checked.

It was agreed upon as "inspection and testing" that I would see more than this certificate, I had suspected it but did not question it. The structural engineer wrote to me that he had to prepare the static calculation and the thermal insulation certificate on behalf of the general contractor and further "according to the Verification Authorization Ordinance (NBVO) I am obliged to supervise the construction work with regard to structural stability," so I commissioned him under the conditions already mentioned.