Install Updates - multiple repository issues

[stevef]

First, try updating again to see if problems 1 & 2  (error 403 and DNS) are still present.
In your case, these were
https://repos.codelite.org/ubuntu
https://repo.skype.com/deb

If the symptoms with these repositories are still the same, you can suspend them using the GUI

Click Menu and begin typing 'Software & Updates' into the search box.
When you see 'Software & Updates' offered as a choice, click on it.

In the window that opens, select the 'Other Software' tab
Look through the list for the references to the repositories that are still causing problems.
Remove the tick from the problem lines.
You will be asked for your password.
Close the window, then retry the update/upgrade process.

All being well, you will be left with the third problem.
https://ppa.launchpadcontent.net/ondrej/php/ubuntu
You will need to give permission for the change as described in post 2.

If you continue to have problems at this point, please repost providing a narrative of the step taken and the results.
If the update/upgrade works at this point, remember you still need to keep re-enabling the problem repositories to check if their problems are fixed (or uninstall the applications)