Slopes and turns
So after two days of practice, I was able to stay on it as long as I want as long as I was going on a mostly straight path. From there I graduated to practicing slopes and turns. It feels bizarre to go up and down slopes, as with a bicycle you are used to your body tilting forwards or backwards. But since this balances you automatically, it doesn't happen and you stay straight up even with slopes. There is some ground clearance, but in very sharp bumps I fear the plastic in the back might hit the ground (never happened).