AI move towards the player in x- axis

hi guy, i am new here and i am new to unity...so my 1st question.. i am working on AI and i am trying to make my AI move towards the player in x- axis the code i can come up with makes it ionstant teleport, how can i make it mre gradual?? any help would be appreciated.

enter code here
var other : Transform;
private var dist : float;
private var speed : float = 0.0;
private var nextFire = 0.0;
private var fireRate = 0.5;
var bullet : GameObject;

function Update()
{

transform.Translate(Vector3(0,0,speed * Time.deltaTime));

dist= Vector3.Distance(other.position, transform.position);

if (dist<40) //start moving
{
speed=10;
}
if(dist<35)//move towards target
{// move in x- axis, the code i have dose instant teleport, how can i make it more gradual???

(other.position - transform.position ).normalized * speed * Time.deltaTime;

}
if (dist<30) //start shooting
{
speed=5;

    if (Time.time > nextFire) {
    nextFire = Time.time + fireRate;
    var clonebullet = Instantiate (bullet, transform.position, transform.rotation);
    }

}

}
enter code here

transform.Translate(Vector3(0,0,speed) * Time.deltaTime);
Also why would speed be the destination.