Unfortunately, the slider isn’t a responsive element. So you’ll see a partial area of the image on the mobile, but not the full image resized.
I’ve checked with some of the other threads the Dev team have responded on regarding this and apparently there’s no work-around to make the slider responsive on mobile devices. The jQuery plugin that is used for the slider doesn’t support it.
You can turn off the slider on mobile devices if required using the options in the appearance>theme settings>slider panel.