I appreciate this method of introducing only one new piece of information at a time. I am not talented at learning languages (reasonable at French, awful at Latin). It has taken five months of daily practice to get to this level. Faster learners can skip levels (provided that they don't make mistakes).
I think this could also work.
staff of the restaurant
In many parts of Duolingo we really have to use the literal translations, so I guessed the same here.
Of course, if this was a part of a whole sentence, we might need 'the' at the beginning to form a correct English sentence.