Im 14 and have a huge belly help?

Hey guys, Im 14 and 200 pounds, I really hate my belly though especially, I've tried everything, and cut out refined sugars and carbohydrates aswelll, but nothing's working. I have started this diet today(how to get a flat tummy in 14 days) I broke the eating plan already by eating a cold pressed fruit bar- no refined sugars and completely natural! My mum said the diet is to hard as it only really consists of green beans, broccoli, chicken, salmon, haddock and turkey and red and green peppers. Please help me, I have also heard that tieing a rope around your tum can flatten it, whenever you release the tum you remind yourself and you suck it back in again. please help, thanks.