The consul asked basic question and if you are really have a real relationship then it's easy to answer. I was nervous of course as I really don't know what to expect or how they are going to "interrogate" me. But honestly, there's nothing really to worry about as long as you're being truthful and honest with your fiancé.
But all in all, they are well organize and nice. The consul who interviewed me is really sweet and soft spoken. There's nothing really to worry if they are very gentle to you.
And of course, being ready before interview date is always better.