It's my exam and in need help I am sure it's reversers current and I don't know my english lecturer say it's no it's provides current I need help please
Actually you are both right.
A motor contains a coil that is free to rotate around a pivot mounted across a magnetic field. When current is applied to that coil the coil generates it's own magnetic field. The difference in angles of those fields causes a force that turns the coil.
If there were no commutator, the coil would oscillate a bit due to it's inertia and finally end up lined up vertically with the magnets.
The commutator is a mechanical switch that, at an appropriate point in the rotation of the coil, sends current through the coil in the appropriate direction.
So, for a simple single coil DC motor, your original answer is correct.
The torque, the force driving the coil around, follows a sinusoidal function as shown below. The maximum torque occurs when the coil is at 90 degrees to the magnetic field and goes to zero when the coil lines up with the field. The left graph below is for no commutator. The centre one is for a single coil commutated motor.
In real DC motors there are multiple coils. The coils are arranged such that the torque curves look like the right hand graph above, a three coil motor. The commutator then supplies current to the appropriate coil at the appropriate angle to keep the torque close to the peak of those curves. One or more coils will be off entirely.
So, yes, the commutator switches current to the coils. It just so happens that the coils are also, eventually, fed current in the other direction after the motor has turned 180 degrees.