If you mean in Star Trek, there have been a couple of recent episodes of Discovery and Prodigy implying that people were speaking native languages translated to English, but before then, there have been plenty of Trek episodes and movies stating explicitly that the characters were speaking English. Realistically, it would be nonsensical for a starship crew to be dependent on computer translation to understand each other. One of the most important parts of training for serving on a starship crew would have to be learning the skills to do things yourself when the tech breaks down. Depending entirely on the tech with no backup plan would be incredibly foolish. And with three or four years spent in Starfleet Academy, that's plenty of time to learn at least one common language.