Hey there, I'm doing German this year as well so hopefully I can provide some insight as to where others are up to. To begin with, I mainly agree with your philosophy that you shouldn't rote-learn answers or rigidly try to stick to a script. However, at the same time, there is literally no harm in preparing some responses for very frequent questions (e.g. what are your hobbies, tell me about your family, what do you want to do after school). In this sense, you should definitely try to do some preparation. The general conversation shouldn't be too hard to control so long as you've practised it sufficiently.
In terms of the detailed study, I'm surprised your school hasn't begun work on it in class already (unless you were being hyperbolic about having said done 'nothing'). I'd at the very least recommend you to get an idea of what kind of topic you're interested in doing. You want to know your resource(s) inside out and be prepared to talk openly about your Schwerpunkt in this part of the oral exam. Perhaps ask your teacher for some more guidance in this regard. Just remember: it's never to late to start preparing for the exams.