Store settings has a new row, Storefront language. It sets the language of the words Magpie adds to your Store: buttons and labels, the cart and checkout, the order, return, review and wishlist pages, most messages to buyers, and the emails buyers get. Dates follow the language. Your own product names, descriptions, pages and policies are shown as you wrote them. English is the default, so nothing changes until you choose another language.
The French, Spanish and German text is a machine translation that a person has not yet reviewed.