How do I unlock the y axis for 2D player movement?,How do I un-restrict my movement along the y Axis?

When creating a movement system for my player character, I unintentionally locked the Y axis for them. When spawning in, they are set to (0, 0, 0) and do not fall to the floor below. How should I edit my code to accommodate for this? The x axis movement works perfect.

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class MoveScript : MonoBehaviour
 {
     public Vector3 position; 
     public Vector2 jumpHeight;
     public float jumpStrength = 5f;
     public bool isGrounded = false;
 
     public float speed = 0f;
     public float acceleration = 5f;
     public float deceleration = 5f;
 
     public float topSpeed = 5f;
     public float topThresh = 1; //Time to get to max speed
     public float stopThresh = 0; //Time to stop with opposite input
     // Start is called before the first frame update
     void Start()
     {
         transform.position = position; 
     }
 
     // Update is called once per frame
     void Update()
     {
         //Jump();
        
 
         if ((Input.GetKey("left")) && (speed < (topSpeed + 1))){
             speed = speed - acceleration * Time.deltaTime;
         }
         else if ((Input.GetKey("right")) && (speed > (-topSpeed - 1))){
             speed = speed + acceleration * Time.deltaTime;
         }
         else
         {
             if(speed > deceleration * Time.deltaTime)
             {
                 speed = speed - deceleration * Time.deltaTime;
             }
             else if (speed < -deceleration * Time.deltaTime)
             {
                 speed = speed + deceleration * Time.deltaTime;
             }
             else
             {
                 speed = 0;
             }
         }
 
         if (speed >= topSpeed)
         {
             speed = topSpeed;
         }
         else if (speed <= -topSpeed)
         {
             speed = -topSpeed;
         }
        
         position.x = transform.position.x + speed * Time.deltaTime;
         transform.position = position;
 }
 }

,I'm trying to create the movement system for my project, with acceleration taken into consideration, but after a couple of tutorials and online help, I've restricted my player character to the x axis. Whenever they spawn in, they are set to (0, 0, 0). The horizontal movement works fine, I just need to add gravity. How should I edit my code to un-restrict the y axis?

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class MoveScript : MonoBehaviour
 {
     public Vector3 position; 
     public float jumpStrength = 5f;
     public bool isGrounded = false;
 
     public float speed = 0f;
     public float acceleration = 5f;
     public float deceleration = 5f;
 
     public float topSpeed = 5f;
     public float topThresh = 1; //Time to get to max speed
     public float stopThresh = 0; //Time to stop with opposite input
     // Start is called before the first frame update
     void Start()
     {
         transform.position = position; 
     }
 
     // Update is called once per frame
     void Update()
     {
         //Jump();
        
 
         if ((Input.GetKey("left")) && (speed < (topSpeed + 1))){
             speed = speed - acceleration * Time.deltaTime;
         }
         else if ((Input.GetKey("right")) && (speed > (-topSpeed - 1))){
             speed = speed + acceleration * Time.deltaTime;
         }
         else
         {
             if(speed > deceleration * Time.deltaTime)
             {
                 speed = speed - deceleration * Time.deltaTime;
             }
             else if (speed < -deceleration * Time.deltaTime)
             {
                 speed = speed + deceleration * Time.deltaTime;
             }
             else
             {
                 speed = 0;
             }
         }
 
         if (speed >= topSpeed)
         {
             speed = topSpeed;
         }
         else if (speed <= -topSpeed)
         {
             speed = -topSpeed;
         }
        
         position.x = transform.position.x + speed * Time.deltaTime;
         transform.position = position;
 }
 }