How do I connect my questions categories to my search results page?

Hi there - I desperately need help.

I would like my search results page to connect to my questions categories.
I have questions like “what counts as a red flag” and I would like this to appear in my search results but when I try to type in “red” into my search bar “no match” is appearing.

thanks - would be very grateful for any adivce!

Here is my public share link: LINK
(how to access public share link)