How would the best way to loose weight quickly ?

Safely: quickly = can occur on any of the crazy crash diets, none of which I endorse. Safely is better. Eat the foods you enjoy but eat less, and move more. Exercise, portion control and increase your intake of filling low calorie foods such as vegetables. They should take up half your plate. Try to eat foods from all food groups such as proteins, fruits, whole grains, low fat dairy, legumes and nuts

Combined: Caloric restriction and exercise. Be careful as rapid weight loss too quickly can set of gallbladder disease and worsen fatty liver disease. Remember as a 20 year old, you goal should be not only losing weight but also establishing a healthy lifestyle that you can sustain for years to come(ideally lifelong)!