Interne Serverfout (Internal Server Error) is a fatal error that has happened and your web server killed the request.
Usually, fatal errors like this are either because PHP times out, or runs out of memory... the underlying error message will be either in your web server's error logs or Craft error logs.
Try editing your php.ini file and increasing the
memory_limit setting to at least 256M, and the
max_execution_time setting to at least 120.
If you’re not sure where your php.ini file is located, create a PHP file called
ini.php alongside your
index.php file with this:
echo 'Loaded php.ini: ' . php_ini_loaded_file();
Then access that file in your web browser by going to
Once you’ve made your changes, restart your web server, restore your database from a pre-update attempt database backup and then try again.