Need Help Adding AJAX to Threaded Comments feature in PHP, Smarty, MySQL, MVC

Hi there. I have an old website (it's currently on PHP 5.6) that was built on the Smarty Template style with an MVC folder structure. I'm going to update it to PHP7.0 or PHP7.3 soon. I have a comments feature with built in replies that used to work perfectly, but I think someone accidentally deleted the AJAX part. I need help fixing it, so it loads the replies instantly and so the image upload works again. I'm attaching some of the files that I think may have parts that affect the comments/replies and screenshots. Note: we built this as a Featured Questions content object which is based on "projects" in my site (projects are basically like a universal post/blog object that can be used for anything and have a project_type). So it's super simple - there's a projects table that basically has all kinds of general content (name, image, description, etc) and we use that to post various types of "content"/objects. We wanted Featured Questions to be more of an object/project so it could have it's own image, category, comments section, users could follow it etc. All that stuff is already built in if I can just get it posting smoothly. Here's the home page: [login to view URL] And this is an individual Featured Question: [login to view URL] I don't want to pay more than $100 for this.