@Sebastian
New lines should be placed to break up equivalent amounts of text to get reasonable spacing. They don't need to be after exact words.
"Packagekit" is a name so it should not be translated, I think "Packagekit-Update-Fehler" is fine, as long as a German speaker (I assume this is German) would understand that "Packagekit" is the name of the thing giving the error.
"{}" followed by a dash should be fine.