If it's only about the width of the layout, then you won't have to bother: The default layouts of SoSci Survey are responsive. That means, you will have a limit (because a questionnaire may otherwise look stupid when it's opened on a 4K screen), but will become smaller when opened on a smartphone.
However, not all question types scale equally good. There are still some issues with scales, and you may have to choose the "automatic" or "dynamic" option for such questions in the display options.