Hello and
I just did some calculating and what you are wanting to do is lose 24 pounds per month. To be very honest I would not tell you how to do that even if I knew, because it sounds extremely unhealthy and dangerous. A healthy weight loss is considered to be 1-2 pounds per week... some weeks it could be more but then again there are often plateaus along the way where ... nothing!! That is very normal. If there was a healthy way to do it as fast as you want, we would all be doing it!
I do wish you all the best on your weight loss journey and would encourage you to get on a healthful eating and exercise program and go for it. But expecting it to happen so quickly is setting yourself up for disappointment and perceived failure when, in fact, you might be achieving huge successes!!
Please don't take this post as discouraging! It is not meant to be at ALL. You CAN do this, and I do realize you are still very young and have not experienced a lot of the ups and downs that a lot of us have.
And

for wanting to catch this so early -- good for you!!!!