Can I give back my adopted son?
Why do you want to give your adopted son back?
Because the kid will get hurt if I'm not able to get married to his mother.
Parent's are expected to look out for the well being of their children, even if they are adopted. You should do whatever is in your power to make right by this child. If you feel best to return them to their mother, make sure you are okay with this decision or you'll live with regret.
I want to do this for myself not for the kid.
That's even worse, and you should have never adopted someone if you didn't want him in the first place. Please reconsider attempting to "give him back" because that would be considered very bad by most people.