Change Language & Region Apps preferences on Mac
On your Mac, use the Apps pane of Language & Region System Preferences to choose different languages for individual apps. For example, even if your system language is English you can have the Messages app display Spanish.
To open this pane, choose Apple menu > System Preferences, click Language & Region , then click Apps.
View the list of apps you’ve set to use a language other than the default language.
Add , Remove
Add and remove apps from the list. When you remove an app from the list, it uses the default language.
Language pop-up menu
To choose a different language for an app in the list, select the app, then choose a language from the pop-up menu.
Open the Input Sources pane of Keyboard preferences, where you can add and remove input sources and set options for input sources.
Select languages to download to your computer so you can translate when offline. You can also enable On-Device Mode to translate on your device even when connected to the internet.