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.
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From the General section, change the language from the drop-down menu.
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You will need to restart it for the changes to take place.
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Upon restarting, the menu and interface will be in the selected language.
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It will not affect WhatsApp settings for mobile devices.
All done.