How long are you staying in Beijing? For about two weeks.
how soon意义为: 多久以后.用在一般将来时,
如: How soon will you be back, Jane? In a week.
how long 意义为:1. (时间)多久,
如:How long have you lived in Shanghai? I have lived there for a year.
2. (物体)多长,如: How long is the rope? It is about 5 metres.