i am not very flexible on my backbone, please sugg

Not everybody is flexible, and it takes a lot of practice to gain flexibility. This is why I would recommend you to practice at least twice a week, ideally with a teacher who can teach you some tricks according to your constitution.

http://s3cr3ty0stg2.wpengine.com/Yoga-for-beginners/How-do-I-start.html

http://s3cr3ty0stg2.wpengine.com/newsletter/12-2008/exercises_maintain_flexible_spine.html

Blessings