Hello bcworkz, thanks for your answer.
Yes you are close actually but I don’t want to trigger the code in my download.php page when the WP page is requested, but I want to trigger it by calling a function from my download.php page in my WP page.
So basically I would like to have more than one page from my plugin to execute functions, like many plugins I have seen out there.
Or do you have any resources to recommend me in order to understand better how a plugin is made (like with filters and actions too), because the official tutorials on wp.com are not really clear to me :/