apt-get update resulted in "Could not open lock file /var/lib/apt/lists/lock - open (13: Permission denied)"

No response to my post yesterday yet. I am thinking it was too long.
This thread contains one part of the earlier thread. One step at a time,right ?
Maybe fixing this is all I need....

maggie@linux ~ $ apt-get update
Reading package lists... Done
E: Could not open lock file /var/lib/apt/lists/lock - open (13: Permission denied)
E: Unable to lock directory /var/lib/apt/lists/
W: Problem unlinking the file /var/cache/apt/pkgcache.bin - RemoveCaches (13: Permission denied)
W: Problem unlinking the file /var/cache/apt/srcpkgcache.bin - RemoveCaches (13: Permission denied)
maggie@linux ~ $

I found a possible fix online and tried it

maggie@linux ~ $ sudo apt-get update && sudo apt-get upgrade
[sudo] password for maggie:
Hit:1 http://security.ubuntu.com/ubuntu focal-security InRelease
Hit:2 http://archive.canonical.com/ubuntu focal InRelease
Hit:3 https://repo.skype.com/deb stable InRelease
Hit:4 http://archive.ubuntu.com/ubuntu focal InRelease
Get:5 http://archive.ubuntu.com/ubuntu focal-updates InRelease [114 kB]
Ign:6 http://packages.linuxmint.com uma InRelease
Hit:7 http://packages.linuxmint.com uma Release
Get:8 http://archive.ubuntu.com/ubuntu focal-backports InRelease [101 kB]
Fetched 214 kB in 2s (87.0 kB/s)
Reading package lists... Done
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
maggie@linux ~ $

There are no errors, yet no fix either. I ran apt-get update again, and it was identical to the first time above...
I found there are some root fixes possible, but I also read one false move in root and I could ruin my system.

#2 Question What is the significance in the E: and the W: ?
#3 And how do I get my terminal results in their own box in this thread ?

I can use some help to fix this. Any takers ? :)