Karachi is 4 hours ahead of Hamburg
Best overlap: 8:00 AM to 2:00 PM in Hamburg is 12:00 PM to 6:00 PM in Karachi.
Plan around 8:00 AM to 2:00 PM in Hamburg, which is 12:00 PM to 6:00 PM in Karachi, to catch everyone during office hours. The overlap is wide at 6 hours, so you can protect mornings for deep work and still find plenty of meeting time. Note that Hamburg follows daylight saving while Karachi stays put, so the times above drift by an hour seasonally.