Please note the following points to prevent the vehicle from rolling back unintentionally on a gradient.
Pull and hold the parking brake switch and press the accelerator. The parking brake will remain engaged and prevent any tendency to roll back down the slope.
You can release the parking brake switch as soon as the engine is delivering enough power to the wheels.
Depending on the weight of the vehicle and trailer and the steepness of the slope, there may be a tendency to roll back downhill when driving away from a standstill.