Need WordPress expert to make a few changes in a website (PHP, HTML CSS)

Hello, There are two issues with our website: ISSUE 1. A shortcode was created to display a list of publications ([materials type="list" filter="members"]). However, it displays the list of publications in one column and we would like it to appear in two columns instead. So we need someone to make changes in the PHP file in order to have a new shortcode that displays the publications in two columns. Note: we've managed to present the publications in two columns by using another shortcode that displays a single publication based on its ID ([materials type="single" id="125"]) and repeating that shortcode for each publication in columns. But we would prefer just using one shortcode. In attachment, you will find the code of the shortcode that needs to be updated. ISSUE 2. On the home page, there is : a) header/menu b) a big banner c) the content..., etc. We can enable and disable the big banner as we please. We will disable it, but we would like to replace it with a layout in two columns like the one in the [login to view URL] file in attachment. Of course, some styling will be added (we will provide photos and example of what we want). We would like everything to be responsive and done in HTML/CSS (not just images). I would like to know how long it would take and how much it would cost to fix each problem (separately, but I would like to work with the same person for both issues, if possible).