Upgrade to 5.6.0.1 error!

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It say's Upgrade to 5.6.0.1 complete! with error put above:

Notice: No translation for the language 'nl_NL' available. in /var/www/wolfsberg.nl/wolfsberg.nl/wwwroot/updates/concrete5.6.0.1/concrete/libraries/3rdparty/Zend/Translate/Adapter.php on line 443
Warning: Cannot modify header information - headers already sent by (output started at /var/www/wolfsberg.nl/wolfsberg.nl/wwwroot/updates/concrete5.6.0.1/concrete/libraries/3rdparty/Zend/Translate/Adapter.php:443) in /var/www/wolfsberg.nl/wolfsberg.nl/wwwroot/updates/concrete5.6.0.1/concrete/core/libraries/view.php on line 899


My live website won't load at all or fully load.
Please help

EDIT:
Seems to work again... But if someone can explain the errors