Pls help with Media Query

HTML-CSS
1

I can’t make the media query on this one.
I’d like to make it so that under 600px width it becames a one-column layout. I tried but i’m not able to make it that way.

2

There may be a better way to do this, but it does display one column, with the navigation above the content.

@media (max-width: 600px) {
 
  header {
    width: 100vw;
    height: 60vh;
    display: flex;
    flex-direction: column;
  }
  
  #navbar {
    height: 60vh
  }
 
  main {
    margin: 65vh 0 0 0;
  }
}