Can't Connect Ethernet modem on Raspberry Pi 4

[MrDreigon]

I’m stuck with the setup on my Raspberry Pi 4.
I have a netgear nighthawk modem connected to the Pi via ethernet.
In Network->Interfaces, eth0 wasn’t even in the interfaces list to start with, I added it from the Devices tab on that page.
I’m not sure if I’ve done this correctly, but it shows it’s sending data.

When I try to setup Speedify it fails saying the device doesn’t have internet.
Can anyone help?
Is there a decent setup guide for Raspberry Pi?

[TalalM]

Hi.
eth0 is reserved for the LAN port.
You need to plug a USB ethernet to the Pi, connected to the modem, the internal Pi port is used as LAN only.

[TalalM]

Old guide that includes the Raspberry Pi 4: Quick Setup - SmoothWAN (archive.org)