How can you flatten your stomach? My belly buldges & sit up are nearly impossible are there any other ways to reach this goal?

Diet AND exercise. Make sure you exercise at least 90 minutes a day, don't skip meals, avoid soda, juice, dairy, alcohol and fried foods. Eat a healthy well balanced diet! also water, organic vegetable broth, green leafy vegetables, natural pickles, apples are great to fill you up so you dont feel hungry and they are very low in calories.