First invoice for earthworks and base slab due

In practice, the construction status report is often a one-page form on which the site manager, for example, marks a cross at [x] Robau fertig and signs at the bottom. The client submits the sheet to the bank, which then releases the funds for the corresponding installment.

One should not expect detailed documentation here unless it has been agreed upon beforehand.

the "execution" is normally not documented by the construction company.

That's right: the execution is regulated in the construction service description or the fundamental obligation to build according to the current state of technology or something similar.