Salut Yves et bienvenue!
Thanks for using our plugins and welcome to the forums!
Don’t worry, your English is good. Likely better than my French. 🙂
I checked your site and I see your issue. Let’s see what can be done.
As a first test, could you switch to a default theme like twentyseventeen and check if the issue still exists with that?
If the issue still exists, then please go through our guide on testing for conflicts.
Thanks and let me know what you find.
Andras