Is it possible to translate the "Add to cart" button in a different language?

You can tune all user interface texts from the app preferences page. Particularly, the 'Add to cart button' text.

Just navigate to the Visual styles → Add to Cart button section to see its customization options.

There, you will be able to translate the text to your store primary language:

For secondary languages, please navigate to the Advanced preferences section, where you will find our Multi-language preferences.