Which bus should I take if I want to go back from North Gate to Tiananmen West Station?

You can take Sightseeing Bus 1 (Guanguang Yixian in Chinese) to Tiananmen Guangchang Xi (Tiananmen Square West) Station. You can also take bus 5 and get off at Zhongshan Gongyuan Ximen (West Gate of Zhongshan Park) Station. After getting off the bus, you will see the Tiananmen West Subway Station. Enter the station and go out through the Exit C to the underground passageway leading to the theater.