First of all you should check if you haven't a connection at all with
Any IP or domain of your choice.
If all packets got lost you have to configure your Network Interface.
To configure your Network Interface you must find out the name of your Interface with:
Your ethernet Interface should look like:
2: enp9s0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
link/ether 00:24:54:c5:f6:f6 brd ff:ff:ff:ff:ff:ff
So here enp9s0
is the name of your Interface, remember that.
Now you have to change a file via sudo with a text editior e.g. nano or vi. I would recommend nano for you.
So login in as root and edit:
Change "enp9s0" to your own interface, that you found out via ip link show.
Now change, ONBOOT=no to ONBOOT=yes, then you can save file by pressing Ctrl+O and close by pressing Ctrl+X.
After a reboot your network interface should work.
You can test it by