Trying to edit the Testimonials Carousel with Elementor, you'll notice that each slide item contains an Elementor template:

The easiest way to access these templates is to mouse-hover the "Edit with Elementor" link on the top Toolbar, locate and click on the Slider 1 - Home 1, Slider 2 - Home 1 and Slider 3 - Home 1 sections

Clicking on it will redirect you to the template's content: 

You can also access the templates from Dashboard > Templates > Saved Templates: 

Make your customizations, following this guide: Guide to Vamtam Elementor Builder

You can repeat the same steps for the "Check out our reviews on Google" section: