You can rename and retype almost everything in any language (with increased character limits). That said, our core functionality text cannot be edited and since much of the RSVP process is part of our core functionality, the buttons and instructions cannot be overridden.
For example, if you enable Guest List Match, the prompt for people to enter their name and email or request access will remain in English. We are working to make the whole site translatable, but unfortunately, this is not an option at this time.
Note: there is no button to switch languages or add pages in different languages at this time. The end result is whatever you have typed in - in any language on any page.