I have adult double scoliosis until 40 degrees i don't know exactly is there anything i can do to reduce the degrees instead of surgery i have a idea, do decompression surgical or not and after wear corset to improve the situation (corset not brace?

Scoliosis is a complex disorder which involves not only bone abnormalities, but muscular adaptive abnormalities in an attempt to compensate. Your Dr who knows your history and your response to various treatments is the best resource for advice on this issue. Ask about non surgical options to see if they are possible in your specific situation.

At 20 your bones have stopped growing and your 40-degree reciprocal curves should remain stable. Neither corset nor brace would be expected to alter the curve at this point, even if you ware it around the clock. If you are symptom free you may want to leave it alone, if not, surgery would be the reasonable option.