Kyphosis(70degree)with lordosis age20 doctors said there's no necessity for surgery they suggest brace and physical therapy can my back became better?

Change is constant: I don't know the specifics of your situation so I can't predict a prognosis for you. However, the body is always changing and responding to the forces being placed on it. Have you explored yoga, in particular Iyengar yoga? Iyengar yoga uses props and pays careful attention to alignment. It is generally considered one of the safer styles of yoga and could be beneficial.