You need to seek the advice of a physician. Avoid self diagnosis.
If you do have gynecomastia is is a hormonal imbalance that needs to be addressed by a physician. Only he can diagnose the problem and treat it properly. Exercises and foods aren’t going to effect gynecomastia because the body is predisposed to deposit fat in that area, regardless. Supplements need to be prescribed or recommended by a doctor. You can do yourself great harm by taking supplements not okay’ed by your doctor. (trust me I’m a nurse).
Sorry I couldn’t give you an easier answer, but I hope this helps.