Unfortunately the quality of the monitor is not that great, I exchanged it with an EIZO CS2740
Quality difference is huge

When starting up, I always have to press the button on the right behind the monitor.
I have a picture

Have you removed the automatic source selection and are you using the monitor with a different cable than before? With automatic, the selection takes forever, without it, it does not find "wrong" sources. Go back to automatic in the menu or to the factory settings.

I mean I have exactly the one described here but the picture is very dark.