3 Responsive Columns Using Flex and Mobile-first workflow

I decided to take advantage of first-child and last-child pseudo-classes to make some changes in the border-radius of my vehicles. I though this way cause I needed to change the border-radius only in the first and last element of the divs using ".vehicle" class. Since the border-radius just change in this both elements.

I thought about using another class for it, but I think this way using pseudo-classes was better. What do u think about it? Should I do it in another way?

Another thing I would love to understand better is the use of more advanced html tags. If u see my code u will see I used sections tag but I don't really know why I should do it and I don't know when I should do it. So, if u have any advice about it, It would be amazing!

I think that's it.