SharePoint 2013 has Web Application with port 2323 I want to know how to duplication this Web Application with its site collection for port 80 as example.
You have to create another Web application on port 80, same configuration (I.e. authentication, general settings, ). Apply all the customization to new web app if any.
Now take the back of site collection from 1st Web app via central admin or powershell.
Now restore it to new web app via powershell.
Repeat this for all the site collections if more than 1.
One thing keep in mind, new web app will have different url, different content database.
Note, you cannot use the database backup as it will throw the site I'd error.