So I am new to Unity and I am trying a little game.

I am getting a few errors; can someone help?
*
Code:*
`using UnityEngine;
using System.Collections;
using System.Collections.Generic;

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

public class Stove : MonoBehaviour
{
    public GameObject rawSteakPrefab;
    public GameObject cookedSteakPrefab;

    void OnTriggerEnter2D(Collider2D other)
    {
        if (other.CompareTag("Player"))
        {
            // Assume the player is carrying a raw steak
            if (PlayerInventory.HasItem("RawSteak"))
            {
                PlayerInventory.RemoveItem("RawSteak");
                StartCoroutine(CookSteak());
            }
        }
    }

    public List <GameObject> CookSteak()
    {
        // Simulate cooking time
        yield return new WaitForSeconds(5f);
        Instantiate(cookedSteakPrefab, transform.position, Quaternion.identity);
    }
}

Errors:
1. AssetsStove.cs(15,17): error CS0103: The name ‘PlayerInventory’ does not exist in the current context
2. AssetsStove.cs(18,32): error CS1503: Argument 1: cannot convert from ‘System.Collections.Generic.List<UnityEngine.GameObject>’ to ‘string’
3. AssetsStove.cs(23,30): error CS1624: The body of ‘Stove.CookSteak()’ cannot be an iterator block because ‘List<GameObject>’ is not an iterator interface type

thanks!

I am trying out Unity (relatively new, 12 years old)