Wow--it sounds like you have an exciting opportunity! The reality is, no one can tell you what business you should start because that is a personal decision. A few questions to ask yourself--What are you passionate about? Is there a need for a service/product in Kampala that isn't being offered, and can you offer it? What can you see yourself doing five, ten, or twenty years down the road?
Ask yourself these questions, and do a little research. Talk to other business owners. Spend some time in different types of businesses. This is an exciting time for you! Good luck.