Hi I the guess the unit you have purchased is second hand and you may not have seen all the sales information and warnings.
These "A frame" mounted movers are fine on solid and most importantly level ground, but they do have limited grip and as such if the caravan is on a slope the jockey wheel can loose grip and the caravan can move uncontrollably representing crush and colision hazard to people and things in the vicinity. Even worse in damp or icy conditions.
Basically if you feel you could not personally stop or hold a caravan on a slope, then its unlikely your mover can do it either. That's why so many of these movers are offered for sale secondhand.
If you must use it, use it with extreme caution. I would suggest you consider cutting your losses and save for a road wheel mover which have far more control and safety.