Error while installing updates on Linux Lite 3.2

[Mr A]

Hi all,
I'm pretty new to Linux and just installed Linux Lite 3.2

Just tried to do a sudo apt-get update from terminal and i do get an error message:

Fetched 1,025 kB in 4s (231 kB/s)                                       
Reading package lists... Done
W: The repository 'http://extras.ubuntu.com/ubuntu xenial Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: The repository 'http://repo.linuxliteos.com/linuxlite xenial Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: Failed to fetch http://extras.ubuntu.com/ubuntu/dists/xe...6/Packages  404  Not Found [IP: 91.189.92.152 80]
E: Failed to fetch http://repo.linuxliteos.com/linuxlite/di...6/Packages  404  Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.


Is that normal?

Someone suggested to ping 91.189.92.152 which seems to work...

Apologies if it's a stupid question, but I am pretty new to Linux so not sure how to solve it.

Thanks in advance for any help you can provide