His name is Stas. We asked him if he was Jewish, and he said "Shalom." He also showed us that he has on his phone some songs by the chassidic singer Mordechai ben David, which we of course sang together.
We gave him a brochure about mezuzah and told him we have some mezuzahs with us if he'd like to purchase one for his home. He said he'll think about it; he's going out of town tomorrow, but when he comes back, he wants us to meet his siblings.
We then invited him to have a drink, and we made a brachah (blessing) together. We showed him all the kosher food we had brought with us, and told him which of them can be purchased anywhere. We gave him a brochure on kosher food. He seemed very interested.
He took us about two blocks away to show us a building that's now a restaurant. It used to be a synagogue.