Here’s the completed dialogue with the appropriate verb forms:
John: Have you ever been to Spain?
Sue: Yes. I went there a couple of years ago.
John: I didn't know that.
Sue: It was before I met you.
John: Who were you with?
Sue: James.
John: James! My brother James? What will people think?
Sue: Nothing. Up until now, I haven't told anybody. Nobody. Never. It's a secret. I love you now.
John: Really, darling? I have never loved anybody as much as I love you.
Sue: That's sweet.
John: Will you marry me?
Sue: Marry you? Well...
Feel free to ask for further practice or examples!