A movie with people speaking Swahili
Swahili was (and still is) a language that people spoke mainly in East Africa. When Bantu people moved into East Africa around 300 AD, they brought their West African language with them. Swahili is a language based on Bantu, with a lot of words from Arabic, Hindi, and other languages brought into it by Muslim and Indian traders and other travelers. Most people who lived in East Africa after about 900 AD spoke some Swahili, although for some of them it was a second or third language instead of their first language. One famous bit of Swahili (for people who don’t speak it) is the “hakuna matata” phrase from the Lion King movie.
In what is now Kenya and Tanzania, Swahili was many people’s first language. But in other places in Africa, all up and down the coast of East Africa, people spoke Swahili as their second or third language, because Swahili was the language people used to communicate with people from other places. Because a lot of people used Swahili without being really fluent in it, they simplified the way they spoke Swahili to make it easier to learn and understand. (This is the same thing that happened to English after the Norman invasion). Some linguists call this sort of language a “creole”, though others don’t.