Hey Marc-Andre,
Sorry for your trouble here. The essence of your problem comes down to the fact that The Events Calendar does not actually generate a proper WordPress page at the main “/events” URL (or, in your case, “/calendrier” :)).
This may seem odd, but it’s actually a smart decision we made to make sure that our calendar works best as a feed of events, especially when there are a lot of them, and to ensure the best functionality possible for all of our date, time, and view filtering.
So the “/events” or “/calendrier” page is sort of “faked” within WordPress by our plugin, and there is not an actual page in the admin that you can edit for this page. If you have manually created a page to try and do this, delete it.
To add information before the calendar, or after, head to Events > Settings > Display in your admin. Scroll to the bottom and you should find fields like in this screenshot → https://cloudup.com/cVHPL4FEjx7
Adding content there should get it to display before your events are listed. Let us know if this helps!
Cheers,
George