Sign.cs

using UnityEngine;
using UnityEngine.UI;

public class Sign : MonoBehaviour
{
    public GameObject dialogBox;
    public Text dialogText;
    public string dialog;
    public bool playerInRange;

    private void OnTriggerEnter2D(Collider2D other) {
        if (other.CompareTag("Player")) {
            playerInRange=true;
        }
    }

    private void OnTriggerExit2D(Collider2D other) {
        if (other.CompareTag("Player")) {
            playerInRange=false;
            dialogBox.SetActive(false);
        }
    }

    private void Update() {
        if (Input.GetKeyDown("Interact") && playerInRange) {
            if (dialogBox.activeInHierarchy) {
                dialogBox.SetActive(false);
            } else {
                dialogBox.SetActive(true);
                dialogText.Text = dialog;
            }
        }
    }
}