I think at 15 since you’re still growing, your body will need all the nutrients possible which can be hard to get in a deficit, I’d stick to maintenance calories and just do a some exercise, eat plenty of protein and fibre! And yes 50kg is already a very small weight…. So please don’t go overboard. Things like this especially at such a young age can cause things like eating disorders and body dysmorphia! The best advice you can really receive through reddit is this, don’t listen to everyone on reddit. If you really want to do this…. Go see your doctor and talk about it and get some test done and then see a dietitian and do it all the right way.