It’s a PAIN to update WordPress. It’s improved over the versions but still today, you need operating systems knowledge to make it happen.
So, if all you need if an insecure, but quick way to update the WordPress plugins and themes of your website, here it is.

cd /var/www/html/yourwebsite.com/wp-content
chmod 777 .
chown -R www-data plugins themes
echo "define('FS_METHOD','direct');" >> wp-config.php