Confused on what to do for Portfolio pages

I’m running into serious issues with a template I bought and trying to update my case studies into it. The template was designed that all the project pages are in CMS, and I just can’t wrap my head around what I should do. (I have watched all CMS related tutorials etc)

I usually just work with static pages, which is what I was hoping to do here. But when I try to delete and disconnect all CMS items, the website starts acting a bit weird. So I feel like I’m stuck dealing with CMS. Each of my case studies have different headings, images, text etc. So I just don’t understand what I’m supposed to do?