For the radio question, I actually left it til last and wrote an epic novel in the time I had leftover... haha. I talked about a point in "my" childhood when I lived in Africa (I've lived in Aus all my life) and my father took me to see a lion who was being put down for mauling a woman. I said my father had influenced me that day because he refused to support killing the lion, though it got him fired, and I always keep a photo of the lion on me to remind me to be nice to animals and brave like my father... which is why I'm at uni studying vet science.
IT WAS GREAT FUN. And I wasn't sure whether to use "Sie" or "du" either, so I just side-stepped the whole way and used passive
And, chillax, peeps! Native speakers don't always top, because while they obviously thrash everyone else in the speaking, sometimes they don't have the English skills which are necessary to do well in German (c'mon, some Aussie kids don't have the English skills necessary to do well in German)... and you don't have to be a native speaker to do Extension. Sure, it helps, but...
As for Extension preparation, I'm just gonna read all the stories again and do some practice responses. We have a German exchange student staying in our house at the moment, so I exploit her shamelessly to mark my practice papers! xD
Anyway, good luck to you all with your German results, the rest of your exams, and Extension if you do it!
xx Sophia