Thanks Paul, all your answers are helpful and works.
It's a long time I wasn't on that website, neither Joomla, so I need to be refreshed 😊.
I did the changes in the custom CSS as you suggested.
And thank you for the CSS edit in Flex, I appreciate.
When applying updates, it is difficult to know where from the glitches comes from: Joomla, SPPB, the template, other extensions ? That is why I'm doing more simple websites nowadays, flat files with bootstrap.
Still, I have the "Home page not found" for which I have to find a solution before putting the website live. Should I ask here, on Applikko or on Joomla Forums ?