Trying to edit the "Projects" section with Elementor, you'll notice that it's a Tabs element, and each tab contains an Elementor template:
The easiest way to access these templates is to mouse-hover the "Edit with Elementor" link on the top Toolbar and locate the tabs' templates:
Clicking on each of them will redirect you to the template's content. Here, you can select the post category for each tab. Make your customizations following this guide: Guide to Vamtam Elementor Builder
Notice:
You can set the category or tag by which you'd like to filter the posts. For instance, all posts with the "Buildings" tag will appear under the "Buildings" projects tab. You can use a post category instead of a tag. See the screenshots below:
You can also access the templates from Dashboard > Templates > Saved Templates > Section:
