Why do you write? For love of literature and the written word.
Why do you write Science Fiction and/or Fantasy? Science fiction and fantasy give the writer two sets of very interesting tools. It would be a shame not to use them.
Who is your favorite author? Your favorite story? O, the impossible question. I don't have a favorite author. Or ten. I love the works of Wolfgang Borchert, Hope Mirrlees, Arne Sand, Mervyn Peake, Anna Maria Lenngren, China Miéville, Mikhail Bulgakov, Tove Jansson, Harry Martinson, William Shakespeare, and Karin Boye, just to name a few, but ask me again tomorrow and my list would probably look completely different. As of writing, I've just re-read Franz Kafka's In der Strafkolonie for the fourth time, or so. It's quite wonderful, so it can be my favorite story of today.
What are you trying to say with your fiction? Depends on what I'm writing. Sometimes I'm trying to say this,
If you could write your own epitaph, what would it say? Being twenty years old, I really do hope that's a premature question.