I’m using the Content Slider module that has a background image for the slides and text overlay which works fine with large screens but when viewed with medium and small screen devices the slides background image and the text are stacked. The background image is on top and the text content stacks below the image.
Unfortunately, that is the default layout for the module. If you want to have it so that your text is still visible on the background image, you will want to use a slider plugin such as Slider Revolution which you can use via the shortcode and HTML module.