need help with custom template

I am trying to customize a theme to look like this page html/CSS:

I have started with the free template themia-lite, and have figured out this much so far:

This is for a client who needs to be able to change out this main "Make A Difference" image, and have 4 columns of ads, instead of 3 and look like the three columns of ads seen here:

I need this one page to be dynamic and responsive. In other words, I need the client to be able to edit the main image, and then... lets say she ads a post with the Title/Image/Text/Link to the post, and have it show up in location column 1. then a second post, same format title/Image/Text/Link and it automatically shows up in column 2, etc... filling up 4 columns and then repeating below each row.

First question, is that even possible?

Second question, if so how do I do that?

this template doesn't have anything dynamic that I can find that allows for this main image or any of these "ads" to be edited, added to, or removed. They are hard-coded into the front-page.php.

The rest of the design can stay hardcoded, as I have it now. I just need some way of making this content area with the white background and currently 3 columns, dynamic so that the client can edit them, add to them, and they will still be responsive.

I tried building this template in Bootstrap, which I'm familiar with, but again, got to this point and couldn't get any farther, as I don't know how to make the content area dynamic or how to give the client the ability to add new ads and keep the columns responsive.

Your help is greatly appreciated.