Please answer my Track question. It is VERY important?

I run track, i have been runnig since last year i am small for my age and i recently suffered a knee injury during basketball season, well i injured it in september but it got better like a month and a half ago. i used to be fast before but now i am not that fast well not fast enough than all of the other girls. I am not a sprinter which is what the coach has me do. last year i ran 800 3200 m relay and sometime 400. he has me run 100s and 200s. I really want him to thing i am a great runner because i really love track and i am determined and have potential. I hope to run in the olympics. any ideas on how to get better quickly and i also have a meet tomorrow what is som good food to eat before it. for dinner i am having a taco and a salad with no dressing anything else?