Centralizing content within a resizing rectangle

Hi community

I’m building a simple hype based webpage and wanted to know if anyone knows of a way to have the grey boxes in my image below to fill the screen horizontally whilst keeping the gaps between them. I would also like to keep the icons (represented by the red boxes) in the middle of the grey rectangles. I have the menu sizing perfectly but thats one object and easy to manage. Im still taking advantage of the breakpoints but i would like to have some dynamic ‘live’ sizing content also.

Sorry for the basic question, I’m not a coder at heart but am being forced to finish this page. This would help enormously if you guys could point me in the right direction.