Unity 2D - Player movement on android is different than on PC

The player on the android version of the game moves "instantly". It doesn't builds up speed or slows down unlike the PC version of the game. There the player builds up speed and slows down if the button isn't pressed anymore. Here's the code:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityStandardAssets.CrossPlatformInput;
 
 public class PlayerPhysics : MonoBehaviour
 {
     Rigidbody2D rb;
     float dirX;
 
     public float speed = 5f;
     public float jumpHeight = 8.5f;
     public float maxSpeed = 5;
     public float fallMultiplier = 5f;
     public float lowJumpMultiplier = 2f;
 
     public bool grounded;
     public bool jumping;
 
     bool facingRight = true;
     Vector3 localScale;
 
     private Animator anim;
 
 
     void Start()
     {
 
         localScale = transform.localScale;
         rb = GetComponent<Rigidbody2D>();
 
         //Animations of the Char.
         anim = gameObject.GetComponent<Animator>();
 
     }
 
     void Update()
     {
 
 #if UNITY_EDITOR || UNITY_STANDALONE || UNITY_WEBPLAYER
 
         dirX = Input.GetAxis("Horizontal");
 
         if (Input.GetButtonDown("Jump") && grounded)
         {
             jumping = true;
         }
 
 #elif UNITY_ANDROID
         
         //Controlls
         dirX = CrossPlatformInputManager.GetAxis("Horizontal");
 
         if (CrossPlatformInputManager.GetButtonDown("Jump") && grounded)
         {
             jumping = true;
         }
         
 #endif
 
         //Animations of the Char.
         anim.SetBool("Grounded", grounded);
         anim.SetFloat("Speed", Mathf.Abs(rb.velocity.x));
 
     }
 
     void FixedUpdate()
     {
 
 #if UNITY_EDITOR || UNITY_STANDALONE || UNITY_WEBPLAYER
 
         if (jumping == true)
         {
             GetComponent<Rigidbody2D>().AddForce(Vector2.up * jumpHeight, ForceMode2D.Impulse);
             jumping = false;
         }
 
         // Jump-Physics
         if (rb.velocity.y < 0)
         {
             rb.gravityScale = fallMultiplier;
         }
         else if (rb.velocity.y > 0 && !Input.GetButton("Jump"))
         {
             rb.gravityScale = lowJumpMultiplier;
         }
         else
         {
             rb.gravityScale = 1f;
         }
 
 #elif UNITY_ANDROID
 
         if (jumping == true)
         {
             GetComponent<Rigidbody2D>().AddForce(Vector2.up * jumpHeight, ForceMode2D.Impulse);
             jumping = false;
         }
         
         // Jump-Physics
         if (rb.velocity.y < 0)
         {
             rb.gravityScale = fallMultiplier;
         }
         else if (rb.velocity.y > 0 && !CrossPlatformInputManager.GetButton("Jump"))
         {
             rb.gravityScale = lowJumpMultiplier;
         }
         else
         {
             rb.gravityScale = 1f;
         }
 
 #endif
       
         //Movement
         rb.velocity = new Vector2(dirX * speed, rb.velocity.y);
 
         //Speed limit
         if (rb.velocity.x > maxSpeed)
         {
             rb.velocity = new Vector2(maxSpeed, rb.velocity.y);
         }
 
         if (rb.velocity.x < -maxSpeed)
         {
             rb.velocity = new Vector2(-maxSpeed, rb.velocity.y);
         }
     }
 
     void LateUpdate()
     {
         CheckWhereToFace();
     }
 
     void CheckWhereToFace()
     {
         if (dirX > 0)
             facingRight = true;
         else
             if (dirX < 0)
             facingRight = false;
         if (((facingRight) && (localScale.x < 0)) || ((!facingRight) && (localScale.x > 0)))
             localScale.x *= -1;
         transform.localScale = localScale;
     }
 }