Beijing is 7 hours ahead of Hamburg
Best overlap: 8:00 AM to 11:00 AM in Hamburg is 3:00 PM to 6:00 PM in Beijing.
Both offices are open during 8:00 AM to 11:00 AM Hamburg time, which is 3:00 PM to 6:00 PM in Beijing. Roughly 3 hours of common time means scheduling is manageable; just avoid the very edges of the window. Just remember Hamburg changes its clocks for daylight saving and Beijing doesn't, so confirm the overlap whenever the seasons turn.