Media Query is not working On Technical documentation project

Can someone help? I am unable to apply the media query. It just doesn’t work on it. can somebody tell me how exactly we use media query?

So if I’m reading your code correctly, your media query states: if the screen is less than 600px-wide, the font-size of the body will be set to 12px.

When I make the preview window less wide (in other words, when I make the screen less than 600px-wide), the media query is, indeed, working.

Media queries are ideal for responsive web design because we want our site to be as accessible and readable on as many (different-sized) devices as possible.

What did you want to do with the media query besides changing the font-size?

Thank you for replying.

What I want is, to be able to read all text clearly when the screen size is 600 px or less. Probably NAV on Top or left and the rest of the text below it. but text just hides behind NAV and can see nothing.