How to lose weight quickly?

… kaii so im 14 years old, I have exactly 15 daiiz till school starts and I know that im not going to lose as much weight as I want before this happens but I’d like to get started. im 130 pounds and im about 5’6. im not really over weight but I’d like to lose a little bit of stomach fat. actually about 15 pounds. now I was running 3 kilometers a daii but when I was in grade 4 I had surgery on mi right ankle and ever since it hurts after a lot of exercise, making basketball and any other sports I like extremely painful, and I had been running for a week when mi ankle started hurting and for two daiiz after I could barley walk. I have had many different doctors look at mi ankle and they all say nothings wrong… WHY DOES IT KEEP HURTING THEN? andive even been for bone scans and stuff and there is still nothing wrong with it. so I duno but does any one have some exercises good for losing stomach fat, with out having to use mi ankle because its so sore!! & im not into lipo lol so please help people :P