How can i disable KEyboard button

Hey there. I have a simple question. I followed a movement Tutorial and just wanted to change some stuff. I especially wanted to change that you cant move left right and back while jumping but my Problem is that I don't know how to disable Keys. It would be great if anybody could help me change the code so that it works

 using System.Collections;
 using System.Collections.Generic;
 using System.Collections.Specialized;
 using UnityEngine;
 
 public class PlayerMovement : MonoBehaviour
 {
     public CharacterController controller;
 
     public float WalkSpeed = 12f;
 
     public Transform GroundCheck;
     public float GroundDistance = 0.4f;
     public LayerMask GroundMask;
 
     Vector3 Velocity;
     bool IsGrounded;
     public float Gravity = -9.81f;
 
     public float JumpHeight = 3f;
     
     
     
     
     void Update()
     {
         IsGrounded = Physics.CheckSphere(GroundCheck.position, GroundDistance, GroundMask);
 
         if(IsGrounded && Velocity.y < 0)
         {
             Velocity.y = -2f;
         }
 
         float x = Input.GetAxis("Horizontal");
         float z = Input.GetAxis("Vertical");
 
         Vector3 move = transform.right * x + transform.forward * z;
 
         controller.Move(move * WalkSpeed * Time.deltaTime);
 
         Velocity.y += Gravity * Time.deltaTime;
 
         controller.Move(Velocity * Time.deltaTime);
 
         if(Input.GetButtonDown("Jump") && IsGrounded)
         {
             Velocity.y = Mathf.Sqrt(JumpHeight * -2f * Gravity);
         }
 
         if(IsGrounded == false)
         {
             Input.GetButtonDown(KeyCode.A);
         }
         
 
     }
 }

greetings

Ruven