I'm 20 years old and still have acne, how to cure acne?

Not curable, man: Acne is a chronic, serious disease that needs to be managed until it remits on its own. Many of your fellow 20-year-olds are still affected but they're caring for themselves. You can do the same. Topical benzoyl peroxide is your best friend; if you're not cleared by this, get with your personal physician. Consider a course of Isotretinoin if your physician agrees. Man up and take charge.