Question about Gigaset C570A Go

Yes, this is possible. All Gigaset devices with the "Go" designation are Internet-compatible. On the one hand, it is possible to synchronise data (contacts) with other devices (mobile phone, PC) and on the other hand, up to 6 IP telephony accounts (SIP) can be operated. For example, you can set up an Australian SIP phone number and then make calls from Switzerland to Australia at the local rate. You can find more details here: https://www.gigaset.com/go

The base station has a purple cable that is connected to the Swisscom box in my case. It does not have RJ45.