W: Some index files failed to download. They have been ignored, or old ones used instead.
I've deleted many http links from the above code I got due to restriction of 5links for new users
The message is telling you that
kw.archive.ubuntu.com is currently down. Try again later.
BTW, post support questions in #general-help.
can't I change it to another server?? I tried to set it on main server but still getting same error.
Software & Updates
Download From, on the drop down menu, select "Main Server"
Reboot and check by running "sudo apt update" in terminal again.
If it is still showing
We can edit your sources.list to change it to
Moved to General Help.