Nairobi is 1 hour ahead of Warsaw
Best overlap: 8:00 AM to 5:00 PM in Warsaw is 9:00 AM to 6:00 PM in Nairobi.
If you set up a recurring sync, 8:00 AM to 5:00 PM in Warsaw (9:00 AM to 6:00 PM in Nairobi) is the natural home for it. Despite the 1-hour difference, a 9-hour overlap keeps things simple and gives both teams breathing room. Remember that Warsaw shifts for daylight saving and Nairobi doesn't, so recalculate the overlap after each clock change.