But the Lord came down to see the city and the tower which the sons of men had built. And the Lord said, “Indeed the people are one and they all have one language, and this is what they begin to do; now nothing that they propose to do will be withheld from them. Come, let Us go down and there confuse their language, that they may not understand one another’s speech.” So the Lord scattered them abroad from there over the face of all the earth, and they ceased building the city. Therefore its name is called Babel, because there the Lord confused the language of all the earth; and from there the Lord scattered them abroad over the face of all the earth.
Genesis 11:5‭-‬9 NKJV

Under the New Testement we are commanded and commissioned by Jesus to:

And he said to them, “As you go into all the world, preach openly the wonderful news of the gospel to the entire human race!
Mark 16:15 TPT

To effectively preach the Gospel we need to be able to communicate. To communicate we need to be able to relate to those in the people groups we are called to reach. This can be by a supernatural means like the day of Pentecost with a manifestation of the gift of tongues or if you know people locally you may be able to use an interpretator or by diligently learning the language, culture and practices of those you are called to reach.

Primarily it’s the indigenous people who reach their people but if we want influence to plant, empower & equip the local body of believers this will happen through effective communication. By learning the languageand culture this also shows respect, humility, genuineness & can confirm a true calling.