Result: Entertain is working properly! I now have absolutely no shocks and no formation of small blocks. I have switched the way even two switches in a row. This is also against a new Netgear GS108E-300PES.
An advantage of both devices is the way that they've been properly configured for telecom Entertain. So I did not need an extra to the configuration menu. Another advantage for me as a Mac OSX or user is that both switches have an online configuration. So if you still want to look at how the switches are configured, only needs the IP address in the browser settings and off you go. The software (Windows only) is therefore not necessary.