B-737-800 First Officer reported uncommanded aircraft movement and confusion during push back when the ground crew disconnected the tow bar and communication from the flight deck before the parking brake was set; due to a language barrier. The Captain set the parking brake and no injury or damage occurred.

Narrative

Completed Pre-flight tasks; boarded all passengers; and obtained permission from ZZZZ Ground to push back from the gate. Ground crew received push instruction from the Captain; and the push began. It became evident relatively quickly that the push crew was not moving the aircraft to the desired location; however; repeated queries as to the push direction and instructions were met with what can only be described as confusion due to an; in hindsight; obvious language barrier. As we were already deep into the push and starting engines; we elected to continue until the ground crew stopped the aircraft and we could talk to them in a more direct manner. I was monitoring the engine start at this point and did not see very much of what was happening outside at this time. The pushback crew stopped the aircraft and asked to set the parking brake; and we tried to tell them again this was not the desired pushback directions and we would need to be turned around. What became evident very quickly is that the pushback crew must have disconnected the tow bar; without receiving confirmation that the parking brake was set; and the aircraft began and uncommanded roll towards the tug and tow crew. The Captain promptly applied the brakes; stopped the aircraft; and announced a stop to the operation for safety. During this few seconds; the ground crew had evidently unplugged the headset; removed the tug and tow bar from around the airplane; gave a wave off (without our signaling of receipt); and walked away from the aircraft. We coordinated an extended pause with ATC; and hailed station ops to explain the situation. After again coordinating with ATC to taxi and be turned in the correct direction; we obtained a wing-walker from local operations and taxied from the gate without further incident. I believe this event was mostly due to a language barrier between the tow leader and ourselves; however; it was an unacceptable degradation in operational safety that very nearly led to a significant incident.