Can't access to system, problem with Main.qml

[wonder]

Ok, yes, now yes, the file is in the location.
My friend, send to me a photo of the file, I view that, Neon backport are activate, Maui Specific Packages Backports are deactivated.
He, are activate the maui specific backport.
Then, sudo apt-get update, and then, sudo apt-get install -f. Any change.
My friend indicate to me that, before activate this backport, he are run sudo apt-get upgrade, is this a problem?

After the activate backport, run install -f and view any change, he run again apt-get upgrade, then, prompt for repository, if change for distribuitor or maintenance original, he select change for distribuitor.

Continue with the problem.

Thanks.