For going to a new scene in Unity:

1) Go to File / Build Settings... and add all your scenes to the list of Scenes in Build.

2) Make a new C#-Script called GoToScene with the following code (but exchange "NameOfTheScene" for the name of the scene you want the script to lead to ):

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

public class GoToScene : MonoBehaviour {
    
    void OnMouseUp () {
            SceneManager.LoadScene ("NameOfTheScene");
        }  

}

3) Attach the script to a gameobject that has a collider (so it will know when you click on it).

For going to a web page:

1) Make a new C#-Script called GoToLink with the following code:

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

public class GoToLink : MonoBehaviour {

public string WebAdress;

 void OnMouseUp () {
      
        Application.OpenURL(WebAdress);
    }

  }

2) Attach the script to a gameobject that has a collider (so it will know when you click on it).

3) Click on the Gameobject with the script and edit the web adress