Translation:We chat beside that restaurant in which there are no guests.
If only the clumsy English translations were consistently clumsy in the same way! I spend far more time focusing on my English than actually learning Hungarian with these lessons. I am losing my mind. Every time I hear Duolingo's wrong answer audio I get that much closer to throwing my laptop into the garbage.
I realize now that Hungarian constructs a single (albeit complex) contruction where in English we would use two simple sentences. Do contemporary Hungarians actually speak this way? I ask because the English translations are nothing any one would say (at least not that I've encountered).
a az etterem - "a az" = that (special form of az az due to the mellett). Just the would be just az etterem. What makes it hard to see is the "mellett" - or easy to see because it is repeated - a mellett az etterem mellett - "next to that restauarant". Next to the restarunt would just have one mellett.
To your latest reply:
Sorry if I was unclear, I meant the az as in a mellett being the marker. It's a bit confusing when both az and a change their appearance when doing grammar. :)
Using "a mellett" is this sentence is necessary, but you can restructure the sentence a little to drop the marker: "Beszélgetünk az étterem mellett, amelyben nincsenek vendégek." In this case you cannot translate it with "that restaurant", of course.
If the relative clause is disconnected from the noun it refers to, you need a marker az and amelyik as a relative pronoun. But there's also the option to restructure that sentence to have the relative clause right after the noun, and use amely instead, and in that case you don't need to use az. vvsey has talked at length about the topic in another discussion. It's really interesting. :)