First steps with a new editor or theme can be challenging but it's worth it.
If you're newbie with Elementor or you're experiencing difficulties editing the theme's demo content, we recommend you to save the page/post as a template prior to customise it: https://elementor.com/help/how-to-duplicate-an-elementor-page/
This way, you can restore immediately the demo content and start over, if something goes wrong.
If you haven't done the step above, and have messed up a page or global template, there's another solution:
Step 1: You have to set up a staging/developing location.
Step 2: Install and set up the theme and demo content.
Step 3: Save the page you need to restore as a template https://elementor.com/help/how-to-duplicate-an-elementor-page/
Step 4: Export the demo page/global template.
Step 5: Import the demo page/global template to your primary installation.