If the sentences have patterns that are readily reapatable. However, do fixed sentences enable you to express your thoughts and idea in a conversation, which is basically improvisation? They will help in certain situations where you can predict the content of the conversation, but beyond that, I think that it will be a bit of a limited approach. Simply readin widely, but with attention to the language used, would probably be more beneficial, IMO. By the way, what's your first language?