With GemPages, the Parallax module mainly serves this function. Besides, you also can create it by selecting the Fixed mode of Background Attachment property to create a similar effect.
When you check the module Parallax on mobile, you will notice that it isn’t functional. The background image will display as a static image and can be cropped as needed.
It’s disabled on purpose since the Parallax function isn’t responsive at its core due to the technical limitations of mobile browsers. Additionally, the scrolling effect itself is quite heavy to load and might cause some slow loading issues or choppy movement for your live page. If the target of your website is mobile-user specifically, you should consider this fact while building your pages.
You can replace the static image of Parallax on Mobile with a Hero Banner or Image with the fitting dimension, GemPages settings allow you to disable the Parallax section on mobile by using Visibility.