Customize Wordpress theme "Cinerama"

I have purchased and installed a WP theme called Cinerama, and I would like help customizing it. The theme includes the editor Elementor, so the freelancer must be familiar with that editor. ***The freelancer must also be familiar with this specific theme, Cinerama, or must be willing to read the documentation.*** This is because it is a fairly involved theme, and I have already had "experts" who didn't understand the theme and who could "do anything in Wordpress" mess it up. Having said that, what I want to do is fairly simple. The theme includes a "portfolio" of posts, each categorized and containing custom features. There is a custom home page displaying the featured images of these posts in three columns, with a category filtering feature at the top. When you click on a category, only the images for posts in that category appear. When you click on the post's image, the post displays full page. I will create the images and the text for the posts. What I don't know how to do is edit all this in Elementor in a way that makes it work. Details on request, but basically I don't know how to change the category display on the three-column page, and I don't know how to add my own categorized posts to the page and exclude the theme demo posts. I also need help editing the Contact and the About pages, but this should be fairly straightforward. Once again, I just don't know how to edit in Elementor (I used WP in the past with much simpler editors).