Simple Pickup and Inventory System | Pickup | Inventory | C# | Unity Game Engine

Item.cs

[System.Serializable]
public class Item
{
    public string name;
    public int count;

    public Item(string itemName, int itemCount)
    {
        name = itemName;
        count = itemCount;
    }
}

Inventory.cs

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

public class Inventory : MonoBehaviour
{
    public static Inventory instance;
    public List<Item> items = new List<Item>();

    void Awake()
    {
        if (instance != null)
            Destroy(gameObject);
        else
            instance = this;
    }

    public void AddItem(Item itemToAdd)
    {
        bool itemExists = false;

        foreach (Item item in items)
        {
            if(item.name == itemToAdd.name)
            {
                item.count += itemToAdd.count;
                itemExists = true;
                break;
            }
        }
        if(!itemExists)
        {
            items.Add(itemToAdd);
        }
        Debug.Log(itemToAdd.count + " " + itemToAdd.name + "added to inventory.");
    }

    public void RemoveItem(Item itemToRemove)
    {
        foreach (var item in items)
        {
            if(item.name == itemToRemove.name)
            {
                item.count -= itemToRemove.count;
                if(item.count <= 0)
                {
                    items.Remove(itemToRemove);
                }
                break;
            }
        }
        Debug.Log(itemToRemove.count + " " + itemToRemove.name + "removed from inventory.");
    }
}

Pickup.cs

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

public class Pickup : MonoBehaviour
{
    public Item item = new Item("Item Name", 1);

    void OnTriggerEnter(Collider other)
    {
        if(other.CompareTag("Player"))
        {
            Inventory.instance.AddItem(item);
            Destroy(gameObject);
        }
    }
}