Since the car is traveling on a horizontal highway, gravity is directed normal to its speed vector and cannot affect it. It would seem that a car with the engine off can move evenly. However, the car is affected by frictional forces from the side of the incoming air, losses on internal friction in mechanisms and rolling resistance associated with deformation of tires in contact with the road surface. All of these factors work to decelerate the car, thus, negative acceleration appears and the car with the engine off does not move evenly, but decelerates.
One of the components of a person's success in our time is receiving modern high-quality education, mastering the knowledge, skills and abilities necessary for life in society. A person today needs to study almost all his life, mastering everything new and new, acquiring the necessary professional qualities.