CSS flexbox project

Hello everyone happy friday from Madrid,

New topic, new problem. I am having issues with flex properties. When I apply it to my div it goes above the margin of the div and I can’t fix it, meaning that I can’t and don’t know how to properly align them how I want. In this case 3 images top and 2 images down inside of their parent div margin. With this said if somebody can take a look at the code and give a hint of what could be wrong here? Thanks!

Flex Box Project link