São Paulo is 5 hours behind Oslo
Best overlap: 1:00 PM to 6:00 PM in Oslo is 8:00 AM to 1:00 PM in São Paulo.
Your shared working hours run 1:00 PM to 6:00 PM in Oslo (8:00 AM to 1:00 PM in São Paulo). You've got a decent 5-hour window. Set a recurring time near 1:00 PM in Oslo (8:00 AM in São Paulo) and stick to it. Just remember Oslo changes its clocks for daylight saving and São Paulo doesn't, so confirm the overlap whenever the seasons turn.