Yes, the router can also be used as a VPN server. I don't know at the moment whether the interface is in German. What I can say for sure, however, is that it is relatively irrelevant, as most configurations (especially the VPN config) should rather be done via the console. This device is therefore not for beginners.

Yes, this router works with Wingo/Swisscom. There is a good manual in the Ubiquiti forum (https://community.ubnt.com/t5...).
The only problem I had was the firmware version. An old V1.7.x was installed. With the Swisscom network, however, it only works from V1.9.x.
I used the SFP module from the Wingo router...