Hi,
I refreshed the theme, and found the mistake. I put a condition in order not to see the footer on my homepage: if( !is_front_page() ) {get_footer();}, and it seems the responsive menu was link to the footer.
So now it works.
Another point: still on the homepage, as i don’t have any header image, there is an important blank between the logo and the image (only on mobile, it looks ok on computer). Any solution to reduce this blank ?
https://www.lempereur-consulting.com
Thanks a lot Manesh.