My problem is solved.
It was indeed a problem related to my brain rather than the component. Lol !!!
In fact I have articles from 5 categories. So To resolve my problem, I created a category grouping these 5 subcategories.
I then created a ghost menu with a menu entry pointing to a category blog that points to Cat_Generale.
I assigned to this menu: Template style, a specific gantry template with only SYSTEM MESSAGE and PAGE CONTENT
Everything works perfectly.
Thank you for your response which put me on the right path.