Hi, Welcome to Health care magic forum.
As you describe, you have irregular distribution of body fat, and short legs, means short stature.
Getting long legs may depend upon the age, if you are less than the age of 18 years, you may try with the advise of an orthopedic surgeon.
He will take the
X ray of the ends of the long bones, and decide whether you can grow long or not.
To have a thin bum, and other parts where the fat is more, you can try in 3 ways.
1-controle taking calories, fats, fries, junk foods and oily foods.
2-Increase the activity of the body, practice
yoga, exercises, morning walk, and do any work in front of you.
3-minimize the sleeping time, practice late to bed and early to rise. Avoid sleeping in the day time.
Wishing for a quick and complete recovery. Thank you.