How do missionaries reach people who speak another language?
Many do it the hard way. They go to school, learn the language, live in the culture, and stay with the people.
Then there are others who have to visit different groups who speak different languages. They can’t learn them all, so they might take an interpreter with them.
We must not forget the Bible translators who go to a given tribal or language group and translate the Bible into their language, staying over a ten-year period. For those who cannot read, we have audio specialists who make recordings of the gospel message. Literature missions print pamphlets in all the major languages in a country and get them to every door.