2. I couldn't listen to the audio but in my opinion, the fact that it was "Susan's parents" who visited Greece is quite important. Simply saying "parents" doesn't show that you totally understood the spoken text and it also wouldn't make a natural English sentence (we don't say "Parents already visited Greece". If you said that, someone would ask "Whose parents?"
3. I have made corrections to your post in red. Please read them carefully. You particularly need to concentrate on your use of articles.
Student or Learner