The flight instructor stated that the student pilot made a stable approach to the runway during an orientation flight. During ground rollout, the airplane veered to the left and the flight instructor stated "I have the controls" on two different occasions. The student pilot did not understand the flight instructor, which resulted in the two pilots "fighting" over the flight controls. The airplane subsequently exited the runway and struck a ditch, damaging the right wing. The flight instructor stated there were no mechanical issues with the airplane.