"Are you going to the subway?"
Translation:Metroya gidiyor musunuz?
In English, "are you going?" is asking if you're going there right now. "Do you go?" is asking if you go there habitually -- for instance, do you go to the subway every day?
Turkish makes a similar distinction between the present continuous and the simple present (officially called the Aorist), but there are some differences, too. A lot of them are explained in Ektoraskan's excellent post here: https://www.duolingo.com/comment/8649253