Sprinting help ???

I am a sprinter and my age is 13+. I am keen to know what can i do to improve my timing for my 100m , 200m as well as my 400m. Pls suggest running drills , workout or other things that will aid in improving my timing for sprinting. Currently, my best timing for 100m is 12.76seconds , my 200m is 26.47seconds and my 400m is 55.33seconds. How can i improve ?