I have kyphosis, i think the curve is 40%. is it possible make my spine straight? if yes, what are the methods? i have no back pain or discomfort.

Spine Disorder: 40% kyphosis is quite significant. Even though you are not presently experiencing pain, it is possible that may occur in the future. Corrective measures are not simple and can involve non-surgical options such as extensive braces and physical therapy and surgical options, which can be fairly major. I would advise evaluation by an expert spine md.

Ortho consult!: It depends on the cause and the severity of the kyphosis. You really need to see a spine specialist for a definitive individual answer.

Muscle conditioning: Great - no symptoms such as severe pain etc. No surgery will make you feel better than what you describe right now. Keeping the paraspinous muscles strong is important - isometric exercises such as stationary bike, rowing machine, yoga, breast stroike swimming etc will keep you healthy for many many years.

Complications?: I'm not sure what "40 % [percent]" means in this context. (How far along until surgery?!). Kyphosis is usually progressive- you may be at 40 degrees (Cobb angle) now, but later on, 50-60-65 degrees or more. At some point, pain isn't the only concern. Breathing problems can develop as the lungs get compressed. PFTs may be needed. Get surgery when you're healthy, not when symptoms develop to up risk