If I eat banana I find acidity and burning in my stomach, and many other things causes this problem what is the cure?

See your doctor. These symptoms can only be adequately worked up by your doctor. He/she will listen to you, perform an examination, perhaps orders some tests to find out what's wrong.
Common acid-related? The possibilities are numerous--ranging from acid reflux (i.e., heartburn) or a peptic ulcer to pancreatic or biliary disease & even stress. Alarm signs include weight loss, bleeding, recurrent vomiting, significant tenderness. Cut back on citrus, alcohol, tobacco (if any), chocolate, fatty or greasy food, fizzy drinks. Avoid nsaid's (advil, aleve, (naproxen) aspirin). Consider Prilosec otc to reduce acid.