What should I know about religions in Africa if im travelling there?

Muslim, Christian, Jewish and traditional beliefs are what you'll find. Take some time to have a cursory knowledge of them before you go. The idea is to know enough not to disrespect anyone.

Also, Africa is a CONTINENT, not a country so you cannot possibly be visiting everywhere! Therefore, narrow your research to the country you are visiting. You can learn about their religion that way.

Sunni Islam is the dominant religion in North and Central Africa. Parts of West Africa just under the Sahara are also mostly Sunni Muslims, as well as the coastal areas in East Africa down to Mozambique. Protestants can be found at some coastal areas of West Africa, as well as in Namibia and South Africa. Orthodox and Eastern Church followers exist in East Sudan, North Eriteria and Northwest and Central Ethiopia. Thr rest of Africa is dominated by tribal religions.