What is the problem here ?( move script, c#, basic, platformer)

Hi guys, I wrote a scrip that moves character horizontal. But its does not work correctly and i didn't see where is the problem :( there is no error about code. And other code that i wrote with physics move is working correctly(error is not respect to my input settings) Hopefully you can help me . Thanks everyone.

 using UnityEngine;
 using System.Collections;

 public class moveTest3D : MonoBehaviour
 {
 
 public float groundRay=10f;
 
 public bool isGrounded=true;
 public bool isSwimming=false;
 public bool isJumping=false;
 public bool isRunning=false;
 
 public float acc=10f;
 public float groundMaxSpeed=10f;
 public float groundJump=20f;
 
 void Start(){

     
 }////////////////////////////start
 
 void Update(){
     
     RaycastHit hit;
     Ray grounding = new Ray(transform.position, Vector3.down);
     Debug.DrawRay(transform.position, Vector3.down * groundRay);
     
     
     if(Physics.Raycast(grounding, out hit, groundRay)){
         if(hit.collider.tag == "ground"){
             isGrounded=true;
         }else{ isGrounded=false;}
     }

 
 
 if(Input.GetButtonDown("Jump") && isGrounded){
     isJumping = true;
 }    

}///////////////////////////update

void FixedUpdate(){

     float horizontalInput = Input.GetAxis("Horizontal");
     float run = horizontalInput * acc;
     
     if(run>groundMaxSpeed){
         run=groundMaxSpeed;
         isRunning=true;
     }
     if(isRunning && isGrounded){
         run *= Time.deltaTime;
         transform.Translate(run,0,0);
     }

}//////////////////////////fixedupdate

}////////////////////////// Mono Behaviour