Please help, by click on the event module i get an error:

Notice: Undefined index: eventid in /var/www/vhosts/feuerwehren-rhein-erft.de/httpdocs/components/com_community/router.php on line 97

what can we do

Hi.

This is not an error but just a php notice. You can disable it:

Backend -> Global configuration -> Server -> Error reporting (set to "Default" or "None").

This notice will not affect your system performance in any way.

But you have other issue with menu items. Here is how to fix it:

When you upgrading JomSocial menu items in JomSocial toolbar lost "connection" with component. Joomla! mark them as disabled and with notice: "Component 'com_community' does not exist". In order to fix it please follow this instruction:

- click on menu item in JomSocial menu in order to edit it
- when in edit mode don't change anything
- save
- menu item should be fixed
- do it for every JomSocial related menu items (if needed) in all other menus