Make grids in html for phone and pc

I'm pretty new to web development and im right now trying to make my website responsive. My first page is already responsive but i can't get my second to be responsive aswell. It might be beacause i use grid or something. My questiton is can i make a second grid that only displays when the screen size is 600px wide or less? I know i can use media queries but i would like the need some more help here. And how do i hide the other grid that's meant for pc?

I have tried using media queries but with no result. I don't know how i remove the pc grid that's the biggest problem for me.