Hello Vivien,
Thanks for writing in!
The example URL is only using the background-attachment: fixed;
property. Please disable the Parallax option in the section setting’s background option and then find the “Customize” tab. Insert this inline element CSS instead:
$el .x-bg > div {
background-attachment: fixed;
}
This trick will only work if your section is a big as your browser window. It might not look good if you have smaller section heights. See the example on the page.
Please note that the code provided above serves as a guide only and is to help you in getting started so implementing it and maintaining the code will be out of our support scope and for further maintenance for new possible versions of the theme that may cause the customization to break, you will need to hire a developer.
Best Regards.