duplicating page templates

When you duplicated the template, I assume that you gave the template file a new file name, and placed it in the same directory as the source. And that you changed the “Template Name” in the duplicated file. And then made changes to the new template file to change the code on the button to point to the desired page.

And then you can edit the page and specify the new template for that page.

And that you did this on a Child Theme, because a theme update will overwrite any changes you made to theme files.

Ask the googles/bings/ducks about Child Themes (there are plugins that will create one for you), and also about Templates and how they work. Some programming skills are needed to understand how templates work.