Typed messages on ChitChat are translated automatically. You write in the language you think in, the other person reads it in theirs, and their reply comes back to you the same way. Nothing needs copying into another tab.
Three things are worth knowing about it. First, it works on what is typed and only on that. A voice on a video call is not translated, which is exactly why the message box on the call matters when the two of you are short of shared words. Second, it is automatic translation, so it is at its best with complete, ordinary sentences. One thought per message, names spelled out, no abbreviations: "what are you doing today?" survives the trip and "wyd" does not. Third, it carries meaning better than it carries jokes. Wordplay tends to arrive flat, while a kind question arrives intact.
If a translated line reads oddly, assume the machine before you assume the person. Ask again in simpler words. Most misunderstandings in a translated chat are one rephrasing away from being cleared up.
Learning the other person's language? Type your attempt, then say it out loud on the call. They get the meaning from the text and you get the practice from the speaking.