Moving Character in direction of camera

Unity Engine
1 
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.SceneManagement;

public class Ball_Controller : MonoBehaviour{
public float speed;
private Rigidbody rb;

    // Start is called before the first frame update
    void Start()
    {
        rb = GetComponent<Rigidbody> ();

    }

    // Update is called once per frame
    void FixedUpdate()
    {
        float moveHorizontal = Input.GetAxis ("Horizontal");
        float moveVertical = Input.GetAxis ("Vertical");
        Vector3 movement = new Vector3 (moveHorizontal, 0.0f, moveVertical);
        rb.AddForce (movement * speed);


    }

    void OnTriggerEnter (Collider other){
        if (other.CompareTag ("LoadLevelTrigger")) {
           
            other.GetComponent<LoadLevelTrigger> ().LoadDefinedScene ();
        }


      if (other.CompareTag ("KillZ")) {
         int scene = SceneManager.GetActiveScene ().buildIndex;
        SceneManager.LoadScene(scene);
        }



    }
}

I am trying to make my character move in the direction the camera is facing. I am very new to coding but I am trying to do this for a games design class I do. All the answers I find never seem to work (or I am doing something wrong without noticing). If anyone can help me that would be amazing! I have attached my character controller.

2

To get camera looking direction: camera.transform.forward;
Use this in your rb.AddForce