Hi @Stefan3 for security reasons WireGuard settings are displayed only once during the creation of the VPN. If you want to save them, you can download the configuration file during the first setup and store it in a safe place. Note that the WireGuard configuration file contains the keys to connect to your Home Network from remote locations, so don't share it with anyone.
Regarding the possibility to connect to the VPN when the VPN is disabled on the Internet-Box, that should not happen. In my experience, on some devices WireGuard App shows the connection up even if it is not. To be sure, you can check the RX statistics on the WireGuard App on your device, you should see 0 pkt received.