I suggest adding a script to allow the user to increase the font size. This functionality is sometimes shown by a box with two different sizes of "A" and plus and minus buttons to increase and decrease. By experimentation, you can figure out how much of an increase is sufficient.
How about using a multi-step form? It looks like you're essentially already doing this, just with an accordion.
Source - Omkar Bailkeri
This would ensure the user always knew they could scroll (gotta get to that "Next" button) and allow the interface to control the flow of the form more easily. The steps could also be clickable, so the user could ...
Two options come to mind for me.
To enforce the visual effect of content being available behind this 'wall', you could work with borders and/or shadows. This is also a rather common way of showing there is more to be explored. You can also look at Material Design to see how they approach this: Material design link on scrolling techniques
You could make the ...
You could add a notification that appears after a short amount of time when the users are not moving anymore which indicates that there is more content to be discovered.
Many websites use this pattern, so users keep scrolling.
It’s usually placed in the bottom middle of the screen and shows a scrolling finger, sometimes animated.