Custom URL not working !

Hello,
when trying to display single Udemy course ID so i can put a custom URL
The Custom URL DOES NOT WORK !
once clicked, it takes us to the Udemy course instead of my custom URL.

here is the scenario :
– I want to display a list of Udemy courses
– each course is displayed with a single ID and Custom URL.

i want to put a custom URL so as to take visitor to a page where he can see the course preview before going to Udemy.

Is there any way i could either :
– make custom URL work.
or make plugin just display course info
and disable Udemy link.

Thank you