WhatsApp for Windows lets you change the menu and interface language.
Doing that is simple, open WhatsApp for Windows and click the bottom-left gear icon to access Settings.
From the General section, change the language from the drop-down menu.
You will need to restart it for the changes to take place.
Upon restarting, the menu and interface will be in the selected language.
It will not affect WhatsApp settings for mobile devices.
All done.