No written order given. Window installed

formal ist es ungenuegend.

Before I start throwing defect complaints around, I try to find a consensus through dialogue. If that does not work for certain reasons, the defect will be reported accordingly.

Before I start throwing complaints around, I try to find a consensus through dialogue. If that doesn't work for some reason, the defect will be reported accordingly.

Hello! The window fitter is laughing at you and not answering the phone! That's the end of the fun.

That sounds nice, but formally it is insufficient

That's exactly the point. The information is incomplete and unstructured. How is one supposed to develop a good negotiation strategy with that? Legally, all is lost if nothing substantial is added. You are right, if the window installer wants to, he will let the OP starve at arm's length. No scolding, threatening, or hitting helps there. Do you have a better alternative than removing emotions and approaching the conversation factually and first goal-oriented, then leading? A confrontation is almost certainly lost. Involving a lawyer increases the damage.

Involving a lawyer increases the damage.

I did not write anything about a lawyer at all.

Properly formatted complaint of defects with a deadline. Otherwise, the window manufacturer will keep laughing at him.

The properly formatted complaint of defects with a deadline is a good tool when no agreement can be reached and remains as a stage - provided no deadlines are missed.

I did not write anything about a lawyer.

Correct. No one claimed that either.