I tried what you say took out some spaces, but it still does not work.
this is the EM:
"Fatal error: Namespace declaration statement has to be the very first statement in the script in /home/eszham/eszter-maura.tk/wp-content/plugins/simple-subscribe/libs/SimpleSubscribe/Frontend.php on line 10"
and the first 11 lines:
* This file is part of the Simple Subscribe plugin.
* Copyright (c) 2013 Martin Pícha (http://latorante.name)
* For the full copyright and license information, please view
* the SimpleSubscribe.php file in root directory of this plugin.
I even tried taking the part between the /* */ out, but the only thing that changed was that the EM mentioned "line 2".
If you have any further ides, I'd be glad for help.