Old PlayerController.cs

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

public class PlayerController : MonoBehaviour {

    public float speed;

    private Rigidbody rb;

    void Start ()
    {
        rb = GetComponent<Rigidbody> ();
    }

    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.gameObject.CompareTag ("Pick Up"))
        {
            other.gameObject.SetActive (false);
        }
    }
}