How did the expansion of both christianity and islam occur in africa

Christianity started spreading in Africa in the first century A. D. It first entered in the continent through Egypt, where it grew rapidly, and then it expanded to the west getting to what today is known as Tunisia, and to the South getting to Sudan and to the Kingdom of Aksum in Ethiopia. Christian Monasticism was born in Egypt, as many religious men went to meditate to the desert. There were several important early Christian leaders from North Africa that influenced the church, like Augustine of Hippo. However, the expansion of Christianity was not entirely peaceful, there were many conflicts in Egypt between Christian majorities - mostly poor people and slaves - and pagan rulers and masters.

Islam, on the other hand, started spreading in Africa since the 7th century, when the Omayyad caliphate - Islamic Empire - conquered Egypt, Libya, Carthage-Tunisia-, and what today is Morocco, entering later in the Iberian peninsula.

After this large conquest, the Christian population in Africa started to decrease, being replaced by Islam in the entire region of North Africa, with the exception of the christian minority in Egypt known as the Coptic Church and some christian populations in Ethiopia. Christianity would reenter Africa during the 19th century due to the work of European Christian missionaries in Sub-Saharan Africa.