Ah... those damned strings
The first two, I can translate in Spanish, but they always appear as untranslated in the next update, so they probably are not working somehow.
The other two (with plural forms) cannot be done, as far as I know, with QTlinguist. You have to edit the file with a text editor and fill the <numerusform> or whatever is called. Download the file for a language with 100% done and copy the syntax.