"No, Tim is an actor, and not a medic."
Translation:Нет, Тим — актёр, а не медик.
Personally, I use Alt+0151 :). Please understand that in this course I just try fanatically to stick to standard Russian punctuation as you would see it in any Russian book. Which, yes, features —, « and ». People in the forums mostly use - and " " instead.
Apart from being optional in Duolingo as vytah mentioned, Duolingo accepts a single dash - just fine if you want to practice using them
The dash is a punctuation convention when there are two nouns that form the subject and the predicate.
"Is" is implied (there is no other interpretation here)—and, well, in English you cannot really omit it.
In Russian, though, "to be" is dropped in present tense sentences of this type (though, it is retained in declarations of existence of something and "I have"-sentences).
Sorry, after i asked this question I saw the tips where this was already explained. Thanks anyway. Your replay made me understand it a little better.