Mobile First Approach Using Flexbox

from about 1025px to 1140px you have elements extending outside the view port causing the scroll bar at the bottom. So you need to change your transition point or try to stack the boxes in a tighter design

if you look at mine you will see I used Grid for the 4 cards as I transitioned to the desktop size. Grid template Areas are really easy and flexible to use when you want to adjust content order but I guess you also could use Flex-Order to try to move a single card container to the other single card container to achieve the same thing just using flexbox https://palgramming.github.io/Frontend_Mentor_Challenges/four_card_feature_section/index.html