Tehran is 2.5 hours ahead of Hamburg
Best overlap: 8:30 AM to 3:30 PM in Hamburg is 11:00 AM to 6:00 PM in Tehran.
Both offices are open during 8:30 AM to 3:30 PM Hamburg time, which is 11:00 AM to 6:00 PM in Tehran. The 2.5-hour gap barely gets in the way — you've got 7 hours of overlap, so pick whatever time fits the agenda. The window above shifts seasonally: Hamburg keeps daylight saving while Tehran ignores it.