HTML, CSS (Flexbox to align most parts) and Javascript,

I would love to get some comments/feedback on my CSS and Javascript solution. It has been a while that I did some basic HTML, CSS and Javascript. In my CSS file I feel I made to much duplication code. In my Javascript file I struggled with the click event. I wanted to toggle an element on click, but i only find a toggle function with ClassList, but not with whole elements with some Dynamic values. Hope someone can give me another solution for what i have found.