Joomla 4: jquery::ui not found

Hello,
As I decided to migrate from Joomla 3.10 to Joomla 4 today, finally I managed to install it but... some things don't work.

In my frontend homepage ( japprecie.fr ):

• The menus are fully developed
• All Flexi-related things don't work. The category view has the error Cannot access protected property Joomla\CMS\Menu\MenuItem::$params

In the backend:

• There's a warning for multilingual: Le module de menu affichant le lien de menu de la page d'accueil ayant l'attribut langue "Toutes" ne doit pas être publié.
  (The menu module displaying the homepage menu link with the language attribute "All" must not be published.)
• When I try to edit the main menu homepage (which is FLEXIcontent >> Category >> Category), I get the error: jquery::ui not found
• When I try to edit any Item, I get the error: Class "CategoryHelperAssociation" not found

I believe all these errors must be linked more or less.
What should I do to solve this all?

Regards,
Hervé

Hello did you update to flexi 4 ? That necessary

Hello,
I didn't know I had to upgrade to Flexicontent 4.
Now I'm done, and it works.
Still a few adjustments to make to my personal configuration though (templates and so on).
Thanks,
Hervé

Cool