No written order given. Window installed

The offer stated a different sliding element than was delivered. So basically wrong, right?

At least you have proof. What is stated in the offer is also what should have been delivered?

The description doesn't tell me anything, I'm not a window expert.

Written complaint with a 2-week deadline for remedying the defect and done.

On the other hand, he also has nothing in hand if push comes to shove.

What should he have in hand or not have? Barroom slogan!
Acceptance of the offer is enough. I find your tone quite unobjective and a bit sneaky – the best thing is to behave correctly, otherwise you make yourself vulnerable (if push comes to shove ;) )

In such cases, it is always good to be on site at the construction site, preferably with an order form or contract. That way, the craftsman won’t even get the chance to install something like that. Always remain friendly and factual when it comes to damages or incorrectly delivered materials. On the construction site, the owner or builder is the boss, not the journeymen from the window construction. But for that, you also have to keep an overview, be constantly on site, and preferably help out yourself.

If the windows are already installed, in my opinion, you bear the burden of proof that the damages were not actually caused by someone else on the construction site. And as far as the wrong color is concerned, it should not be a problem to check the order form/contract and then complain or revoke in writing. Except, of course, if the craftsmen and the windows were PARTICULARLY cheap and there is nothing in writing.

The offer stated a different sliding element than was delivered. So basically wrong, right?

Is that really the case?
I couldn’t really tell exactly so far. What deviates from the offer (color, unspecified rail?)? Is the offer available in writing?

I see the damage to the running rail as a cosmetic defect. That’s annoying. Still, it’s not worth more than €100.
The best solution, provided it can be proven and is true, would be an exchange due to the alleged wrong delivery. Although some can also laminate on site...

The description is not structured. Remove some emotion and add objectivity. It helps now and in case of a dispute anyway. What I understood: There is an offer. There is an acceptance (oral). Work was carried out. The work does not correspond to the offer. There are objectionable damages. An invoice has not yet been issued. Quite a normal complaint, usually unproblematic in a calm tone. Try to remove the emotions with the window fitter and restart communication. If you cannot do that, it will definitely lead to a dispute. If the window fitter cannot do that, at least you have taken a chance. Usually, craft entrepreneurs are quite pragmatic and easy to deal with, as long as you have not annoyed them for a long time beforehand.

The description is not structured. Take some emotion out and add objectivity. Helps now and in case of dispute anyway. What I understood: There is an offer. There is a confirmation (oral) Work was carried out. The work does not correspond to the offer. There are reportable damages. An invoice has not yet been issued. Quite a normal complaint, usually unproblematic in a calm tone. Try to remove the emotions with the window maker and restart the communication. If you can’t do that, it will definitely lead to a dispute. If the window maker can’t do that, you’ve at least taken a chance. Usually, craftsmen are quite pragmatic and amicable as long as you haven’t annoyed them for a longer time before

I think I read that there wasn’t even an order, neither written nor oral... exclusively an offer that was discussed on site to clarify details of the offer? Question to the OP: Is that correct?