how to work my game

Ok Im a highschooler and I am working on a game in unity where a sphere moves down and around a tube controlled by you to avoid obstacles. I am trying to make it so that the ball can move forward at a designated speed but you can control how the ball moves sideways. I thought about using waypoints for this but the ball is acting very jerky. Also the tube twists and turns. Ive been stuck on this for a while all possible answers are welcomed. Thanks ahead of time. var currentWP: int = 0;

 //the array of waypoints in order of visiting
 //can be made up of any game objects
 var waypoints: GameObject[];
 
 var speed: int = 5;
 var rotationSpeed: int = 2;
 
 //how close to get to the waypoint to consider having reached it
 var accuracy: Number = 5;
 
 function Update () 
 {
     if(waypoints.length == 0) return;
     if(Vector3.Distance(waypoints[currentWP].transform.position, transform.position) < accuracy)
     {
         currentWP++;
         if(currentWP >= waypoints.length)
         {
             currentWP = 0;
         }    
     }
     
     //rotate towards target
     var direction = waypoints[currentWP].transform.position - transform.position;
     transform.rotation = Quaternion.Slerp(transform.rotation,Quaternion.LookRotation(direction), rotationSpeed * Time.deltaTime);
     transform.Translate(0, 0, Time.deltaTime * speed);
 }