Construction delay - What rights do you have?

What does the contract say about that?

You are the client for the scaffold, so you have to bear the payment for the standing time of the scaffold. As already mentioned, the scaffolding company is not interested in whether and why there have been delays in the use of the scaffold. The delay and the associated additional costs for the scaffold should be reported to the construction company; whether this is advantageous, I will leave undecided...

Now my problem: We have finished building the ground floor and have scheduled the installation date for our ceiling and stairs on 8/8.

Now, quite precisely. You have finished building the ground floor? No, you haven’t, since supports were missing and you knew that. Then, knowing about missing components, you ordered the scaffolding. You could have waited until all the material was there. A very simple matter: Your problem. The developer will say that you haven’t completed your self-performed work. You could have waited until all necessary parts were there. Or what exactly does the contract say? You don’t write anything about that. You don’t answer any of my overall questions and expect a concrete answer to an incompletely described situation.

Huh, how can you write so much nonsense at once, inform yourself first. I even wrote whom we are building with, there is a lot of info material and it has nothing to do with unusual construction projects. You buy a kit, that’s like when you buy a cabinet at Ikea and in the end a screw is missing and you can’t continue building.

Do you mean me? Then get used to a proper tone. And for example Ikea. Even there you can’t just order the craftsman who is supposed to install Hi-Fi or something else in the cabinet if you know that the cabinet is not functional and the installation is not possible.

I understand it so that you received an appointment from the construction company for when the scaffolding is needed. You had it set up accordingly, and now they need it later after all. And the whole thing again a second time. That means you are bearing additional costs because they do not deliver as agreed. I would also be clearly in favor of them bearing the additional costs. But presumably, quite a few things would need to be clearly documented for this.

I understand it as you have received an appointment from the construction company when the scaffold is needed. You had it set up accordingly and now they need it later after all. And the whole thing again a second time. That means you are bearing additional costs because they do not deliver as agreed. I would also clearly be in favor of them bearing the additional costs. But presumably, a lot would have to be clearly documented for this.

Finally someone who understood it

The fact remains that our contractor ordered and delivered parts too late, which caused the delay....

Then it depends on what was agreed in the contractor contract regarding late delivery of parts and subsequent delays including claims for payment. Did you have something like that included in your contract? If not, you have to live with/pay the costs until the following sentence applies.
This kind of thing runs through all positions, starting from possibly toilet rental, construction power meter, crane rental, scaffold rental, apartment rent, standby interest, delayed acceptance of offers from other trades, and a recalculation, etc.

To my knowledge, contractors have standard contracts where it is defined (with exclusion clauses) from which month after the start of construction compensation for damages due to construction delays must be paid.