Hey, nicolinaa!
Welcome to the forums
To add to all the amazing support in the above posts, I would also like to say that debating and public speaking are both great at encouraging a healthy growth mindset that transfers well to all aspects of your life. I did debating in Year 6 but then stopped until Year 9 in which I continued it all through the rest of my high school career. I have a huge tendency to beat myself up after something goes wrong which I'm still working on but I always came out of a debate feeling like I've accomplished something. Even when I was struggling with my arguments or just having a bad round in general, my team was there to carry me through to the end so I would definitely recommend doing it as an extra-curricular activity and make your final years memorable!
As for some practical advice, I would strongly advise you to read widely, engage in the news and stay informed. Debate topics are grouped based on categories such as education, politics, the media etc. Your school's debating coach will have a schedule that usually provides an indication of the categories for each debate you'll be having. Having background knowledge of the recent issues in those areas can assist you in formulating effective and relevant arguments in the debate. I also used to memorise about ten statistics related to those areas (and would pray that one of the topic choices would grant me the opportunity to actually use them) to provide some more logos in my discussion. If you do Legal Studies, this is something you are already probably doing as part of your subject so draw from your knowledge of the content and keep exploring social issues with curiosity and scrutiny
If you are worried about the speaking aspect of it, you could potentially request to be a fourth speaker/team advisor. Fourth speaker doesn't have a speaking role (except for thanking the opposition for the debate at the end) but they are constantly writing speech content for the team both in the preparation room and during the debate. You'll learn lots about debating at a senior level from assisting the team and coming up with rebuttals against the opposition. This can also ease you into the whole experience of debating, rather than throwing yourself into the deep end
Debating roles are also incredibly flexible. My sister started out as a fourth speaker and now she’s first speaker in the school team. I also went from being second speaker to third speaker after realising I liked to have the final word and solidify my team’s case. If you observe the debate and realise you would love to try out a speaking role in a future debate, that should be more than possible for you, your team and your debating coach to arrange
Hope that helps and feel free to ask any follow questions if you have any!
Angelina