OK. If I understand you correctly, what you want to do is to remove the left hand (empty) sidebar and have the main content occupy the space currently occupied by the main content plus the left sidebar.
The first thing to do is to remove the sidebar and see what the result looks like.
Since this is a static home page, WP will load front-page.php if it exists, or index.php if it doesn't (see the WP Template Hierarchy).
If you have a front-page.php file, you need to remove the call to
get_sidebar() in that page (or a page called by it). If you don't have a front-page.php file, the easiest thing to do is probably to create one and copy in the contents of the index.php file and then remove the call to
It's really important that you do all this in a child theme, by the way, if at all possible.
When you've made your changes the sidebar will no longer appear on the home page. If the layout looks OK, then we're done. If it doesn't, we may need to mess a bit with the CSS to get it displaying properly.