Could the next question be gotten not only by manual scrolling but also perhaps by clicking a button in the bottom-right corner of the screen?
There is no concept of next question - all questions within a specific section/group are shown together in a continuous space. Depending on your device screen size, types of questions (simple text which takes only one line vs single choice with many choices) users end up seeing different number of questions at the same time and whatever doesn’t fit to the current view needs to be scrolled. (even this part changes when some enablement condition may show or hide additional questions in the current visible area).
So the only logical place where you have real ‘previous’ or ‘next’ navigation is when entering or exiting a section/group, and there are buttons for those actions in the bottom.