Is newtons first law about acceleration and deceleration
No, Newton's first law, also known as the law of inertia, states that an object at rest will stay at rest, and an object in motion will stay in motion with the same velocity, unless acted upon by an external force.
Acceleration and deceleration are related to Newton's second law, which states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass.