I love your english... You sound like one of the french knights from Monty Python and the 'oly Grail...

Seriously, take a look at your webmaster group. Being the Admin user, it is possible that you have somehow been removed from the webmaster group. The hack cares only about group membership.

As for the script not cleaning up old forums? No it leaves everything in place, but creates a new table that you must populated with forum group access rights.

Fatal error: Cannot redeclare saveaccess() (previously declared in /var/www/html/ressources/modules/mydownloads/include/functions.php:138) in /var/www/html/ressources/include/groupaccess.php on line 105

In forum preferences you are using :
Permission Assigned by - Groups
Hide private forums from users without permission - Yes

You have a private forum to which two groups have access:
Webmaster, comite.

When you who are the site admin look at the site, you cannot see the forum, When you add yourself to the comite group, you can see the forum.

include_once XOOPS_ROOT_PATH . '/modules/mydownloads/include/groupaccess.php';

function checkPermission($groupid, $usersid)
{
global $xoopsUser;

if (!$xoopsUser)
{
$grps = array(XOOPS_GROUP_ANONYMOUS);
$uid=null;
}
else
{
$grps = array_merge( $xoopsUser->getGroups(), XOOPS_GROUP_ANONYMOUS);
$uid = $xoopsUser->getVar('uid');
}
$groupid = explode(" ", $groupid);
for ($i=0; $i<count($groupid); $i++)
{
if (@in_array($groupid[$i], $grps))
{
return true;
}
}

$usersid = explode(" ", $usersid);
for ($i=0; $i<count($usersid); $i++)
{
//echo $usersid[$i];
if ($usersid[$i]==$uid)
{
return true;
}
}
return false;

}