How can i make my backbone straight?

See your doctor: First you should see your doctor to check exactly how 'crooked' it is. You will need a physical exam and X-rays and then a decision can be made if treatment such as bracing needed.

Depends: Do you "slouch" or have scoliosis? Posture requires mental focus until the bad position habits are unlearned. Scoliosis usually requires bracing / physical therapy (and in extremes, surgery). Talk to your Dr or a Physical Therapist for an assessment to start.