Which bus/ subway or train to take to badaling great wall and how long is the travel time?

Bea, you can walk from your hostel to Zhangzizhong Road Subway Station, take subway line 5 to Yonghegong Station, change subway line 2 and get off at Jishuitan Station. Then get out from Exit A and walk toward east to reach Deshengmen Bus Station. There you can take no.877 to reach the wall. It takes around 40 minutes to reach Deshengmen and 1 hour and 15 minutes to the wall.