Responsive social proof section using HTML, CSS FELXBOX, and CSS GRID

Community, I need your help.

What I found difficult while building the project? I found it difficult to implement background images for each device(responsiveness). How do I put two images and background. Also, the favicon imahe, where am I to put it?

Which areas of my code am I unsure of? I am not so sure about the margins and padding.

Questions about best practices? While etsting the HTML markup, it mentioned something about a missing heading in the second section. Kindly look through and tell me what else I am missing.

Thank you.