what i have to do to make my character move up and down in the x Axis?

i want to make my character move in In all directions. what am I doing wrong?

using System.Collections; using System.Collections.Generic; using UnityEngine;

 public class Player : MonoBehaviour {
     private Rigidbody myrigidbody;
     [SerializeField]
     private float movementspeed;
     private bool Attack;
     private bool Slide;
     private bool facingRight;
     private Animator myAnimator;
 
 
     [SerializeField]
     private Transform[] groundPoints;
     [SerializeField]
     private float groundRadius;
     [SerializeField]
     private LayerMask whatIsGround;
 
     private bool isGrounded;
 
     private bool jump;
     [SerializeField]
     private float JumpForce;
 
 
     public float Movementspeed
     {
         get
         {
             return movementspeed;
         }
 
         set
         {
             movementspeed = value;
         }
     }
 
     void Start() {
         facingRight = true;
         myrigidbody = GetComponent<Rigidbody>();
         myAnimator = GetComponent<Animator>();
     }
     void Update()
     {
         HandleInput();
     }
 
     // update is called once per frame
     void FixedUpdate ()
     {
         float horizontal = Input.GetAxis("Horizontal");
 
 
         isGrounded = IsGrounded();
 
         flip(horizontal);
 
         HandleMovement(horizontal);
 
         HandleAttacks();
 
         HandleLayers();
 
         Resetvalues();
 
 
     }
     private void Resetvalues()
     {
         jump = false;
         Attack = false;
         Slide = false;
     }
     private void HandleAttacks()
     {
         if (Input.GetKeyDown(KeyCode.Space))
         {
             jump = true;
         }
         if (Attack && !this.myAnimator.GetCurrentAnimatorStateInfo(0).IsTag("Attack"))
         {
             myAnimator.SetTrigger("Attack");
             myrigidbody.velocity = Vector3.zero;
         }
     }
     private void HandleInput()
     {
         if (Input.GetKeyDown(KeyCode.LeftShift))
         {
             Attack = true;
         }
 
         if (Input.GetKeyDown(KeyCode.LeftControl))
         {
             Slide = true;
         }
 
         if (Input.GetKeyDown(KeyCode.Space))
         {
             jump = true;
         }
 
     }
     private void HandleMovement(float horizontal)
     {
 
         if (myrigidbody.velocity.y < 0)
         {
             myAnimator.SetBool ("land", true);
         }
 
         if (!myAnimator.GetBool("Slide") && !this.myAnimator.GetCurrentAnimatorStateInfo(0).IsTag("Attack"))
         {
             myrigidbody.velocity = new Vector3(horizontal * Movementspeed, myrigidbody.velocity.y);
         }
         if (Slide && !this.myAnimator.GetCurrentAnimatorStateInfo(0).IsName("Slide"))
         {
             myAnimator.SetBool("Slide", true);
         }
         else if (!this.myAnimator.GetCurrentAnimatorStateInfo(0).IsName("Slide"))
         {
             myAnimator.SetBool("Slide", false);
         }
         if (isGrounded && jump)
         {
             isGrounded = false;
             myrigidbody.AddForce(new Vector3(0, JumpForce));
             myAnimator.SetTrigger ("jump");
         }
         myAnimator.SetFloat("speed", Mathf.Abs(horizontal));
     }
     private void flip(float horizontal)
     {
         if (horizontal > 0 && !facingRight || horizontal < 0 && facingRight)
         {
             Vector3 theScale = transform.localScale;
             theScale.x *= -1;
             facingRight = !facingRight;
             transform.localScale = theScale;
         }
     }
     private bool IsGrounded()
     {
         if (myrigidbody.velocity.y <= 0)
 
             foreach (Transform point in groundPoints)
 
             {
                 Collider[] colliders = Physics.OverlapSphere(point.position, groundRadius, whatIsGround);
                 for (int i = 0; i < colliders.Length; i++)
                 {
                     if (colliders[i].gameObject != gameObject)
                     {
 
 
                         myAnimator.SetBool("land", false);
                         return true;
                     }
                 }
             }
 
         return false;
     }
 
     private void HandleLayers()
     {
         if (!IsGrounded()) {
             myAnimator.SetLayerWeight (1, 1);
         }
         else
         {
             myAnimator.SetLayerWeight (1, 0);
         }
     }
 }