Nextcloud very slow on raspberry pi 4 model B

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1

Hello,
I install nextcloud 22 on Raspberry pi 4 (/var/www/nextcloud) with ubuntu 20.04 mate.
All works fine, but it’s very very slow. I followed the instructions about opcache, and this doc: https://docs.nextcloud.com/server/22/admin_manual/configuration_server/caching_configuration.html.
I moved the nextcloud and mysql database folders to a hdd. It’s better if I browse my files directly in the folders, but If I use the dashboard, clicking on Contacts, calendar, etc, the load takes at least 40 seconds…

The output of my config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):

  GNU nano 4.8                                          /var/www/nextcloud/config/config.php                                                   
<?php
$CONFIG = array (
  'instanceid' => 'kkkkkkk',
  'passwordsalt' => 'ddddddF',
  'secret' => 'dddddddd',
  'trusted_domains' => 
  array (
    0 => 'localhost',
    1 => 'xxx.xxx.0.150',
    2 => 'xxx.ddns.net:90',
  ),
  'datadirectory' => '/var/www/nextcloud/data',
  'dbtype' => 'mysql',
  'version' => '22.2.0.2',
  'overwrite.cli.url' => 'http://localhost/nextcloud',
  'dbname' => 'nextcloud',
  'dbhost' => 'localhost',
  'dbport' => '',
  'dbtableprefix' => 'oc_',
  'mysql.utf8mb4' => true,
  'dbuser' => 'xxx-xxx',
  'dbpassword' => 'xxxxx',
  'installed' => true,
  'memcache.local' => '\\OC\\Memcache\\APCu',
  'maintenance' => false,
);

Thank you for your help.