Hello @GabriellePi333 - You cannot assume Udemy will automatically promote your course. It will depend largely on how many other courses already exist in the particular topic area, that are highly rated. If there are many, it just makes sense Udemy will promote those courses and not a new one because Udemy is more likely to earn revenue from an established course rather than a new course.
More than likely you will have to do your own promotions until your course gains some traction and Udemy notices it.
