@BerNet First of all, thanks for both replys. I already tried to setup a VLAN like in https://www.tp-link.com/de/support/faq/788/ explained, but it does not work. I wonder a bit why, cause this is...

Dear Community, I have troubles setting up VLANs, maybe you can tell me how to do it correctly. My Infrastructure is: Modem in Bridge Mode wired to Router Router with enabled DHCP wired to Port 1 -...