dark_classic theme Top menu…

Is there a way for me to remove the top menu from dark_classic theme and replace it with a “drop-down” menu? OR…cut and paste/alter the code for drop-down…say code from defusion theme? I know there IS a way…could someone point me in the right direction. I managed to get “two” menus…uggh! lol by cutting and pasting. I put it back to default dark_classic and am “still” trying different things.
Please help and advise.
Thank you.
Sincerely,
David M. Sellers