I have started a book but I am having a problem on the characters because of the number in the book.
I need to track them and keep them in the right place.
There are at least 12 characters or more. Should I reduce the number?
If you are not an experienced writer, this can indeed pose a problem.
If your characters don't serve major parts or don't serve major purposes, you may cut them, yes. I can't honestly say since iI have no idea who these characters are or the parts they play or how significant they all are.
That's going to be up to you. Start small. Once you master that, you can move up in character and plot development.