Are you asking about using a language other than english in the modeler? Or how to build an application that has functionality to translate an African language?
For the first one, you can change the language of the modeler in the project settings. Here is the documentation for that.
Section 5 is about languages.
If you are trying to build an application that can translate languages, you can probably accomplish that by integrating with the google translate api. I quickly checked and saw that it supports rest services.
Here is the documentation for the google translate api
Here is some documentation on consuming a rest services in Mendix.
and the link to the learning modules to help you get started with the basics in the modeler.