How do I find the parent of a child born 1840 VA who does not match the DNA of his census father?

I’m having a difficult time trying to find out about my Cherokee indian roots as I do know my American indian great grandmother was “adopted” into my family informally, her name changed to Olive, and became christian. Does anyone know of anyone or any group that can help my research.

I would like to find out about my ancestry but I dont know how to go about it because my mom’s people came from India and my dad’s people came from Africa