iTranslate Converse
As you can guess by its name, iTranslate Converse is a great app that will help you translate any conversation to almost any language.
There are almost 40 different languages to choose from, and you can switch between them whenever you need. You can use the Apple Watch app to listen to someone speak and then make the app translate it in real-time.
Then, whenever you need to say something, you can speak to your Apple Watch and translate it into a different language so the other person can understand you.
If you travel a lot or are trying to learn a new language, this app will fit great on your Apple Watch.