Is there any fast losing weight method for a 15 year old?

Gradual is better. Weight loss should be gradual. It will happen automatically with life-style changes such as aerobic exercise, and eating healthy: avoiding sugars, all sodas, ice-cream, juices, starchy vegetables, all refined processed carbohydrates (bread, pasta, rice, etc). Control your portions, eat 5-6 small meals a day, never eat past 6-7:00pm, drink plenty water, fresh fruits and vegetables, and lean protein.
No..... Short of cutting off your arm, there are no safe ways to lose weight rapidly at your age. Rapid weight loss usually means you dehydrate yourself, and this can lead to passing out, heart problems, digetive problems...The list goes on. Ask yourself why you really need to lose rapidly - who or what is so important that you would risk your life. Then, is that worth it? My guess is no!