This is the answer:

From the admin_manual:
https://doc.owncloud.org/server/7.0/adminmanual/configuration/bigfileuploadconfiguration.html

OwnCloud comes with its own owncloud/.htaccess file. Set the following two parameters inside this .htaccess file:

php_value upload_max_filesize = 16G
php_value post_max_size = 16G

Change this values in the .htaccess and restart apache2 again.

mentionable:
In the php.ini you should also increase:

 max_file_uploads 
 max_execution_time