Hamburg is 6 hours behind Jakarta
Best overlap: 2:00 PM to 6:00 PM in Jakarta is 8:00 AM to 12:00 PM in Hamburg.
2:00 PM to 6:00 PM in Jakarta is when Hamburg is also working, at 8:00 AM to 12:00 PM their time. Roughly 4 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 Jakarta doesn't, so confirm the overlap whenever the seasons turn.