How to lose 85 pounds in a year?

Im 14 years old, 5,3 and 185 pounds. My quinceañera is next year and I want to be able to find a quinceañera dress that I love without worrying about sizing. I was 200 pounds before and lost 15 pounds in a 3-4 months. I want to lose all the weight before my birthday next year which is the 6th of June. That will be when my quinceañera will take place m. I also just want to feel much more comfortable in my own body. I can never go out and buy clothes at a mall. I want to lose this weight to be able to be normal like every one else. So anything can help. I can only change my portion sizes because my parents cook the food we make. I am also very picky. Any exercise tips and motivation will be very helpful. Thank you.