Business theme has inbuilt features for Superfish Drop down menu. No additional module is required.
Theme will display your Drupal Main menu in header menu bar.
Administration >> Structure >> Menus >> Main menu
So, make sure you have links in Main menu.
To make drop down menu work, make sure you have enabled Show as expanded for every parent menu
Making drop down menus available in Drupal 8 go to:
Administration >> Structure >> Block layout
Select the menu block and click on Configure and then select the Menu Levels settings according to your needs.