Ok, I did some further investigations and found out that I have a IPv6 Address and that ipv4 is only available via DS Lite / CGNAT, so I cannot use the IPv4 protocol. However, I tried to change the settings in the VPN manager to "IPv6 only" but I cannot get the connection to be active after adding a peer. It will always reset after a few seconds and is inactive again. What can cause this behavior? With the "IPv4 + IPv6" setting I can set the connection to active but I still dont have internet access or access to any device in the network (from my phone with ipv6 address).