(SOLVED) Update Mgr - Error Messages

I suddenly am experiencing difficulties in updating Netrunner installed to my laptop computer. The error messages pertain to refreshing the list of updates. I am uncertain on how to implement corrective action and request assistance. Similar topics offered by this forum don’t seem to be related.
Enclosed are screenshots which may be useful for analysing this issue. Thanks.

There seems to be a problem with the file /var/lib/apt/lists/deb.debian.org_debian_dists_testing_main_binary-amd64_Packages file. Maybe you could try removing this broken file and run
sudo apt update again in a terminal to see if that fixes the issue.

This task was a bit outside my comfort zone and hope you concur with the command I used for removal of the package file:

karl@laptop:~$ rm -r /var/lib/apt/lists/deb.debian.org_debian_dists_testing_main_binary-amd64_Packages
rm: remove write-protected regular file ‘/var/lib/apt/lists/deb.debian.org_debian_dists_testing_main_binary-amd64_Packages’?

Followed by:
karl@laptop:~$ sudo apt update

The update process appeared to be successful.
I pressed the ‘refresh’ button in the mint-update manager and it indicated that the system is up-to-date also.

Great that it worked for you.