Can you adjust the difficulty level ?

Yes, both the GoBalance Play and GoBalace Sport boards are adjustable.
The GoBalance Sport comes with an inflatable cushion.

The GoBalance Sport board itself can be placed on top of any balance element like a Bosu or with the provided balance cushion.

The GoBalance Play is compatible with an inflatable bagel cushion, also adjustable for balance level comfort. If you want to challenge yourself more, increase the amount of air within the tube. If you want to lower the level of difficulty, release a bit of air out of the tube.