I have scoliosis. Now I have a big pain at my back maibe because I work at my desk 9h/day seeting of the chair. What can I do? Can be worse then pain?

Sitting back pain. Scoliosis is only associated with back pain about 16% of the time, but poor posture hurts 85%! i agree that the sitting is the likely cause of your pain. A pmr doctor or physical therapist can assess your posture relative to the desk, and an x ray of your spine will give information on the type of scoliosis you have and act as a marker to assess changes over time. This can be helped!
Aggravates your curv. Pain most common at the apex of curve and aggravated by sitting without support of the apex of the curve. A better chair to support the back and allow tilt back function.