ItemPickup

using System.Collections.Generic;

using UnityEngine;

public class ItemPickup : MonoBehaviour
{
    public Item item;
    private Inventory inventory;
    private InventoryUI inventoryUI;

    private void Start()
    {
        inventory = FindObjectOfType<Inventory>();
        inventoryUI = FindObjectOfType<InventoryUI>();
    }

    public void PickUp()
    {
        Debug.Log("Picking up " + item.name);

        Item foundedItem = inventory.items.Find(inventoryItem => inventoryItem.name == item.name);

        if (foundedItem != null)
        {
            foundedItem.amount = 5;
            inventoryUI.UpdateUI();
            inventory.Add(item);
        }

        Destroy(gameObject);
    }
}

public class InventoryUI : MonoBehaviour
{
    public void UpdateUI() { }
}

public class Inventory : MonoBehaviour
{
    public static Inventory instance;
    public List<Item> items;

    public void Add(Item item) { }
}

public class Item : ScriptableObject
{
    public int amount;
}