Generally, aerobic exercise can reduce body fat, but the accumulation of chest fat is very sensitive to its own hormones. If estrogen secretion is strong, aerobic exercise will not shrink the chest. I can't teach you how to shrink your chest. You'd better consult a doctor. I suggest you do some chest exercises. Lighter ones can do bench presses and birds to make the chest muscles stronger, so that they can hold out their chests and won't look bad because their chests are too big.

Barbell bench press and dumbbell bird, these are the same as men's fitness equipment, but you should keep your weight in a group of 15, not too heavy, and move slowly. Muscle and fat are two substances and cannot be converted. Breast size is related to diet, lifestyle and heredity.