[In attesa di conferma] Default language

I built the website in Greek. After completing it, the client told us they want English as the default language. I installed WPML and set English as the default language. However, when I open the pages, all pages that contain Greek content appear as if they are in English.
How can I fix this?
Could I set Greek as the default language, translate the pages, and then switch the default language back to English? Or is there another way?