Has this parquet flooring been installed properly?

Hello 11ant,
thank you very much for your reply.
Yes, unfortunately it is as you describe it.
Back then, when the trade was completed, I unfortunately had a lot on my plate.

About the company:
The boss runs a training company and also works for well-known companies in the area.

The invoice is attached. The sad thing about the matter is that a product, which was paid for expensively and is supposed to last for many years, was processed so disrespectfully. In some places, lines were drawn with a pen instead of a pencil.

some time ago,

That was 2021, so 3 1/2 years ago.

How do you think I should proceed

I would have long since worked on the finishes myself (with acrylic), especially on the frames, so that I have it nice.
You can probably also very well conceal this line with putty before I get annoyed about it for more years.

Hello ypg,
thank you very much for your contribution.
Yes, that was at the end of 2021.
I believe there is a warranty period of five years?
I am now trying to make the best out of it so that it hopefully still looks okay.
It would be great if the company realizes that the result is not okay and requires rework.

The problem is that there were already many complaints beforehand and I don’t know where to start and where to stop.
When the acrylic/silicone turned yellowish, it became even more noticeable.

When I joined the forum here, I was advised to contact here with you.
Would someone of you please inform ?

The problem is that there were already too many complaints before, and I don’t know where to start and where to stop. When the acrylic/silicone turned yellowish, it became even more noticeable.

When I joined the forum here, I was advised to contact here with you. Would someone among you please inform ?