You have to talk to the guard at the bridge. After that, go to the barrier area next to the nightclub.

As for the side quests, the Joy quest can be continued by simply going back to the Safehouse apartment building. She's waiting outside the apartment door. For the pizzas, there's 3 in middle square, 2 in the housing block (one is inside a house), 3 in the East part of the Living District, 1 next to The Arena Guild, 1 inside one of the apartments next to the safehouse. The one inside the apartment and house are probably the easiest to miss.