Responsive news homepage using CSS Grid and Flexbox

I mostly had trouble with aligning the items in my main tag using Grid. The image for the main story would not fill the whole grid cell. I managed to solve this by making that particular section a flex container and setting the images flex growth to 1. Not really sure if that was the best way to go about it, so I'm really looking for feedback on best practices or things I'm doing wrong that could be improved. Thanks so much :)