I've entered apt-get update like a million times, and never had a real problem until today.
This is the results when I use the "apt-get update" command:

$ sudo apt-get update
[sudo] password for jar:
Hit:1 http://security.debian.org/debian-security stretch/updates InRelease
Ign:2 http://mirrors.edge.kernel.org/debian stretch InRelease
Hit:3 http://mirrors.edge.kernel.org/debian stretch-updates InRelease
Hit:5 http://mirrors.edge.kernel.org/debian stretch Release
Hit:6 https://updates.signal.org/desktop/apt xenial InRelease
Ign:4 https://dl.bintray.com/etcher/debian stable InRelease
Get:8 https://dl.bintray.com/etcher/debian stable Release [3,674 B]
Hit:8 https://dl.bintray.com/etcher/debian stable Release
Get:9 https://dl.bintray.com/etcher/debian stable Release.gpg [821 B]
Ign:9 https://dl.bintray.com/etcher/debian stable Release.gpg
Fetched 821 B in 0s (831 B/s)
Reading package lists... Done
W: Target Packages (main/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list.d/signal-xenial.list:1 and /etc/apt/sources.list.d/signal-xenial.list:2
W: Target Packages (main/binary-all/Packages) is configured multiple times in /etc/apt/sources.list.d/signal-xenial.list:1 and /etc/apt/sources.list.d/signal-xenial.list:2
W: Target Translations (main/i18n/Translation-en_US) is configured multiple times in /etc/apt/sources.list.d/signal-xenial.list:1 and /etc/apt/sources.list.d/signal-xenial.list:2
W: Target Translations (main/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list.d/signal-xenial.list:1 and /etc/apt/sources.list.d/signal-xenial.list:2
W: Target DEP-11 (main/dep11/Components-amd64.yml) is configured multiple times in /etc/apt/sources.list.d/signal-xenial.list:1 and /etc/apt/sources.list.d/signal-xenial.list:2

I am suspicious that I entered the newer command "apt update" about a week ago before installing a program, but I don't know enough about the new "apt" commands to know what happens when it's used. So, someone please tell me what to do to correct this problem please? Thanks in advance for checking me out!sh

You'll notice all errors point to xenial. When you right click on the web address for "Hit:6 https://updates.signal.org/desktop/apt xenial InRelease" and open on another page you will get "Page not found". Either the address is incorrect or doesn't exist, or you need to add a specific/proper GPG key for the site.
BTW, xenial is a Ubuntu name, not Debian stable, mixing packages from different distributions will break Debian, you should have a Debian stable updates mirror in your sources list.

2 members found this post helpful.

Please paste the output from the following command so that we can have a look at your sources:

As Brains says, you should *not* be mixing Debian and Ubuntu repositories. Also, your use of apt was not the problem.

2 members found this post helpful.

$ for i in /etc/apt/sources.list{,.d/*}; do echo file: $i; cat $i; echo ====; done
file: /etc/apt/sources.list
#

# deb cdrom:[Debian GNU/Linux 9.5.0 _Stretch_ - Official amd64 NETINST 20180714-10:25]/ stretch main

# deb cdrom:[Debian GNU/Linux 9.5.0 _Stretch_ - Official amd64 NETINST 20180714-10:25]/ stretch main

deb http://mirrors.kernel.org/debian/ stretch main
deb-src http://mirrors.kernel.org/debian/ stretch main

deb http://security.debian.org/debian-security stretch/updates main
deb-src http://security.debian.org/debian-security stretch/updates main

# stretch-updates, previously known as 'volatile'
deb http://mirrors.kernel.org/debian/ stretch-updates main
deb-src http://mirrors.kernel.org/debian/ stretch-updates main
====
file: /etc/apt/sources.list.d/bk-stuff
cat: /etc/apt/sources.list.d/bk-stuff: Is a directory
====
file: /etc/apt/sources.list.d/etcher.list
deb https://deb.etcher.io stable etcher
====
file: /etc/apt/sources.list.d/etcher.list.save
deb https://deb.etcher.io stable etcher
====
file: /etc/apt/sources.list.d/giuspen-ubuntu-ppa-disco.list
====
file: /etc/apt/sources.list.d/giuspen-ubuntu-ppa-disco.list.save
====
file: /etc/apt/sources.list.d/signal-xenial.list
deb [arch=amd64] https://updates.signal.org/desktop/apt xenial main
deb [arch=amd64] https://updates.signal.org/desktop/apt xenial main
====
file: /etc/apt/sources.list.d/signal-xenial.list.save
deb [arch=amd64] https://updates.signal.org/desktop/apt xenial main
deb [arch=amd64] https://updates.signal.org/desktop/apt xenial main
====

Thanks hydrurga and Brains for checking me out!
Would it be safe to say I have to delete these file:

file: /etc/apt/sources.list.d/giuspen-ubuntu-ppa-disco.list
file: /etc/apt/sources.list.d/giuspen-ubuntu-ppa-disco.list.save
file: /etc/apt/sources.list.d/etcher.list
file: /etc/apt/sources.list.d/etcher.list.save
file: /etc/apt/sources.list.d/giuspen-ubuntu-ppa-disco.list
file: /etc/apt/sources.list.d/giuspen-ubuntu-ppa-disco.list.save
file: /etc/apt/sources.list.d/signal-xenial.list
file: /etc/apt/sources.list.d/signal-xenial.list.save

Also, if I uninstall Kgpg will it remove all the "Release.gpg's"?
When I installed Kgpg just as it completed the install I changed my mind about using it, so I never configured it or set it up completely?
I was waiting on an answer on my post before I tried to change anything.

I don't know when I would have mixed in the Ubuntu repositories, it's not something that I would knowingly do! It will be really nice if you can help me out of my mess! Thks sh!

My /etc/apt/sources.list.d folder is empty. I would delete those for sure as they aren't applicable.
I don't have kgpg installed and have no issues getting updates or installing packages from Debian mirrors.
Make sure to run command: apt-get update after deleting the files.

There is no harm as such in having additional repos in /etc/apt/sources.list.d. However, it is always best when you have problems like this to simplify things. Therefore, now that we know what you have in there, you should delete all the files in that directory (you could have moved them elsewhere as backup but they're easily reproducible in your case). We can always have a look at each repo and figure out what you actually need for the relevant software after you've got apt working again - for example, I use a different repo for Etcher. If the bk-stuff directory is empty then delete it too.

Purely for info, a sample sources.list file (which appears fine in your case): https://wiki.debian.org/SourcesList#...e_sources.list

Note that it's better for you to include any output or code within CODE tags (see https://www.linuxquestions.org/quest...og.php?b=36313).

hydrurga, thanks for taking the time to help me out, see my last post, I think I am now out of the woods so to speak. If you all will check me out one more time!
I get what your are saying about the CODE tags, I'm not quite sure I understand how to use it. But, will work on it for next time. I can see where it is definitely needed!

Brains, thank you so much for helping me out! See my last post, and check me out!

hydrurga, Brains, okay, checking over everything you both suggested. I went in and renamed the file /etc/apt/sources.list.d to xxxsources.list.d

Then I ran apt-get update, and this is what the results is::

$ sudo apt-get update
Ign:1 http://mirrors.edge.kernel.org/debian stretch InRelease
Hit:2 http://mirrors.edge.kernel.org/debian stretch-updates InRelease
Hit:4 http://security.debian.org/debian-security stretch/updates InRelease
Hit:3 http://mirrors.edge.kernel.org/debian stretch Release
Reading package lists... Done

Please tell me that's what it should be looking like!
I try to run apt-get update before every install/remove, and I never give it a second though unless it tell me there is some error.
So.... do you think it's okay to do an install now or not, Thanks again?sh

Absolutely. Looks good, if there were any updates available they would have been listed after "Reading package lists... Done"

1 members found this post helpful.

Alright! Thanks a million, I feel better now....... go linux!

I don't know which version of apt-get you are running but that isn't normally the case for apt-get update. The OP should now run sudo apt-get upgrade to ensure that any upgradeable packages are upgraded.

On the other hand, the newer application apt (as in sudo apt update) *does* provide info on whether there are any upgradeable packages once it has synchronised the package data.

The OP also removed some external repos that relate (perhaps) to packages installed on their system. The Etcher one, for example, can be replaced. If you would like to work through those repos, decide which software they related to, and find the relevant repos for your system then please let me know.