Hamburg is 2 hours behind Moscow
Best overlap: 10:00 AM to 6:00 PM in Moscow is 8:00 AM to 4:00 PM in Hamburg.
10:00 AM to 6:00 PM in Moscow is when Hamburg is also working, at 8:00 AM to 4:00 PM their time. Hamburg is 2 hours behind Moscow, and with 8 hours of overlap you can even run back-to-back calls without stepping outside business hours. Just remember Hamburg changes its clocks for daylight saving and Moscow doesn't, so confirm the overlap whenever the seasons turn.