@Fabiozzo
thanks for contribution
>… can I mesh the swisscom router with the existing google wifi?…
Will somehow work… Does it have to be the (expensive) Google part?
Why not the (cheaper) WLAN Box 2 from Swisscom, which works optimally with Internet-Box 3 and extends the WiFi at least equally well? What can the Google part do that the WLAN Box 2 cannot?
WLAN-Box 2 and WLAN-Box - Help | Swisscom
So it is better not to use a repeater ((½ bandwidth) connection to the router + connection to the WLAN device) than an access point (WLAN device with Ethernet connection to the router (Internet-Box 3)
“Google Nest Wifi is the brand new mesh WiFi system from Google. It consists of a router and one or more access points and replaces your previous WiFi router. The Google Nest Wifi access points extend the coverage in your home and also function as speakers with integrated Google Assistant. ”
A router behind the Internet-Box 3 is by no means entirely trivial. I suspect that devices that then go into the network via this WLAN have no access to devices that are connected to the Internet-Box 3 and vice versa. Is that really what you want? I would also use the WLAN Box 2 first and configure it as an AP.