Generally speaking, it is best to have the solar panels facing North as this would generate the most power throughout the year. However, since Tanzania is so close to the equator the orientation does not matter that much. The period in which you consume most of the energy has a slight effect. For example, if your peak in consumption is in December you may want to orientate the panels South. In case you mainly use electricity in the afternoon, or when you are located in a microclimate with lots of cloud cover in the morning you might want to orientate your panels to the West.
The optimal pitch in Tanzania is 10-15 degrees. The reason behind this is that the panels are cleaned by rain. When putting them flatter, dirt could accumulate on the panel.