Though the size of breast depends on various factors like genetics , body mass and proportion, fat contents and physical activity etc. and hence It Is multifactorial . Similarly treatment or breast reduction or sagging breast reduction also depends on the various factor. Some of Hormonal therapy may be advantageous.There are oils which needs to be massaged on alternate day , and medicine to be taken will tighten the sagging or loose skin and makes it look firm and beautiful  . Surgery can be the last option if not improve with medicine.

No creams

Breast exercises and supporters are usually beneficial

you can learn some yoga and exercise from youtube.

No such creams which are useful