Functionality of browser "back" button

Hello Very Helpful Community! I am new to all of this, if off-and-on struggling for many long hours over the last few months still counts as “new.” Either way, I still don’t know what I’m doing, but I have gotten tremendous guidance and help from previously-posted questions in this forum. Maybe I missed it, but I can’t find a prior thread exactly on point, so for the first time, I’m posting my own question.

My front page is an index of my posts. It contains both author links and article links. These all work properly. But once on the linked-post, the browser “back” button doesn’t return to the front page. Instead, the first click of the back button moves you deeper down into the post you are on. The second click of the back button takes you out of the site. The problem is the same in Chrome, Firefox, Microsoft Edge, my Microsoft phone, and an old droid phone.

I am running the Literatum theme which offers three options for a front page: “mosaic” “3-column” and “list.” I am using “3-column” (which you can’t discern if you are viewing on a phone). There are three separate php files for some things, depending on the option chosen. For example, there are three “elements-frontpage-design” php files and three “elements-loop” php files. There is only one “functions” php file.

I assume I need to make a code modification in the “elements-loop-3columns.php” file or the “functions.php” file.

In searching for a solution, I have found the following lines of code:

<button onclick="window.history.go(-1)">Back</button>

<input type="button" value="Back" onclick="window.history.go(-1)" />

I’m guessing this code needs some question marks and brackets or something and needs to be in a location I haven’t yet pinpointed, because I have played around with it and end up with errors and white screens.

Particulars: WordPress 4.4.1 running Literatum theme which uses AJAX navigation and JS. Minimal plugins, all deactivated and reinstalled with no difference at any point in the process.

Site: heartagree.com

Thank you in advance for your help!