social proof section master using flexbox and custom properties

Hello Guys, I would be grateful for every recommendations and suggestions that can make me improve in Web developpement.

On the other hand I have some questions that do not concern this project directly. I'm a big fan of advanced selectors in css. But I dont know if some of you guys rather use BEM instead of. I just want to know what practice is the best between advanced selectors and BEM. I like advanced selectors cause with them I can avoid the use of several classes. I also know the advantages of BEM but I dont know if this worth it to learn this.