I want to find out if my users understand the website navigation.
To do this, I ask my single select question:

If visitors answer “Yes,” no further question needs to follow. My goal is achieved—I know that these visitors understand the navigation. Of course, I can still ask why they find the navigation understandable.
If they answer “No,” I ask a follow-up question:

In the free-text response, visitors can explain why they are having difficulty with the navigation on the page.