thanks four your reply :). I checked if there is some white-space (you mean in the design.php am I right?). Here is the code of the design.php – I think the problem is, that the design.php starts with the following code:
I have one problem with it and I think it belongs to my theme and my not existing php-skills :). Perhaps you can help me? I was searching for a solution the last two days, but without success. So I will try my luck here.
I tried to activate the plugin over wordpress and in a second step I copied the needed code to my child themes functions.php, but I always get the following error:
Warning: Cannot modify header information – headers already sent by (output started at …/wp-content/themes/theme/design.php:2) in …/wp-includes/pluggable.php on line 876
I found some solutions for such errors, but nothing works for me.