object reference is required to access non-static member 'GameManager.CompleteLever()'

[rajhansuttamksirsagar]

I am trying to follow one online tutorial to make a simple game. and I am getting this error
object reference is required to access non-static member ‘GameManager.CompleteLever()’

using UnityEngine;
using System.Collections;

public class PlayerMovement : MonoBehaviour {
public float moveSpeed;
private Vector3 input;
private Vector3 spawn;
public float maxSpeed;
public GameObject deathParticles;
void Start () {
spawn = transform.position;

}


void Update () {
    input = new Vector3(Input.GetAxisRaw("Horizontal"),0,Input.GetAxisRaw("Vertical"));
    if (GetComponent<Rigidbody>().velocity.magnitude < maxSpeed)
    {
        GetComponent<Rigidbody>().AddForce(input * moveSpeed);

        
    }
    if (transform.position.y < -3)
    {
        Die();
    }
}
void OnCollisionEnter(Collision other)
{
    if (other.transform.tag == "Enemy")
    {
        Die();

    }
}
void OnTriggerEnter(Collider other)
{
    if (other.transform.tag == "Goal")
    {
        GameManager.CompleteLevel();
    }
}
void Die()
{
    Instantiate(deathParticles, transform.position, Quaternion.identity);
    transform.position = spawn;
}

}

[Malleck666]

I assume GameManager is a script?

You’ll need to create an instance of it and assign it in the inspector.