Partial withholding until the trade is fully completed.

Hello everyone, I need a brief legal advice on whether my approach is allowed. A trade at my single-family house has now been completed. The invoice from the general contractor (GÜ) arrived and I withheld the amount except for 1,000 euros. The reason is that leftover waste still needs to be cleared. For me, a trade is only completed when the construction site has been properly left. It is also explicitly stated in the construction service description that all trades commissioned by the GÜ must take their waste with them. Of course, I could have mentioned this directly in the payment. But I neglected to do so. Now, of course, the question arose as to why 1,000 euros are missing. Before I reply, I wanted to quickly ask for your opinion. Thank you

That was the wrong approach at first, you first communicate "Craftsman, please clean up your trash," if nothing happens then you announce "I will withhold x euros if you don't clear your stuff by day y," and if still nothing happens then you can withhold it. 1000€ sounds a bit disproportionate though, or what else is lying around?

I can't tell you whether that is legally allowed, but I think simply withholding money without saying anything is not okay. In my opinion, that's just not proper.

After receiving the invoice, I would have first sought a conversation, if necessary in writing, if the trash is not removed or if there have been problems in the past. How much and what kind of trash are we talking about here?

Of course, I should have announced it. But I am annoyed that the things were just left there and that nothing was done on the GÜ side to ensure that the things were put away. It’s not a gigantic amount. But working like this is also inappropriate.
The total amount was over 30,000 euros. The 1,000€ is probably too much as well. It arose somewhat out of emotion due to lack of communication. Next time, of course, I will announce it. I will also apologize for it.
I have already announced that I am asking to remove certain things. The feedback was that I would receive a response. However, this has not happened until now.

What leads you to conclude that after each "trade" or before each invoicing the trash must be removed? It is not uncommon to collect packaging, remains, etc. and then dispose of them all at once. With us, there was a brief sweeping every day, but the "trash" was stored in one room and eventually picked up together.

To my understanding, everyone who caused the trash takes it with them again. The structural builder takes his trash. The roofer takes his trash, etc. But of course, it could be that the company will clean everything up in the end. Due to a lack of information policy, I decided to proceed this way out of emotion. I will, of course, handle this differently in the future. Thank you for the feedback.