RSS feed full content

Hi,

I am using your theme on my blog http://www.parkwelten.de (feed URL: http://www.parkwelten.de/feed) and I want to see the full content of a post in my feed. Unfortunately, I only see the excerpt. I deactivated the plugins I thought that might cause the issue, but it’s still there. So I am wondering if something in the theme causes this behavior.

Hope you can help to get me where I want to go, even if the issue is not caused by the theme.

thanks in advance
Michael