Adding categories to the homepage

I am creating a Speaker Directory, and my question is about https://https://yoffiespeaks.com/new-homepage/

Is there a way to create a drop-down list for each category on the home page?

I have a section called: “Select a Topic and Find Experts.” Under it is a list of categories. I want to replace that list with categories I created (Business, Health, Religions, etc.) and when someone clicks on a category, I would like for there to be a drop-down list of sub-categories (branding, career advancement, etc.) When someone clicks a sub-category, I would like it to take the person to a page of speakers who match that category.

Thank you.