This is a chat translator mod that uses the google translate API and modifies the chat, so that you can:

Translate every message to your target language just by clicking on it (even ingame)
Send messages in a specified language
Scroll the vanilla ingame chat using the mouse wheel

If you are having scaling issues (e.g. you are running 21:9) or the mouse is a bit off when trying to click in-game, try my mod Ultrawide Fix. Despite its name it could fix your issue even when you are playing on 16:9.

Usage:

Translate incoming messages:

Select the desired language in the mod options
Hover over a message and click to translate
Click again to toggle between showing the translated and original message
It will show the detected language code in parentheses next to the players name.

Translate your outgoing messages:

Type: tl <langauge code> <message>
Generally you will be answering players in their language, so just use the detected language code from their translated message.
Example: tl en hallo -> hello