Perhaps the error was the trailing slash at end of my string (www.domain.com/new-name), because in the content I had links such as www.domain.com/old-namewpcontent/uploads/2013/05/image.gif. Undo the changes didn’t worked.
I tried to install a fresh copy of WordPress in the new folder and take over all files, theme and database tables. This didn’t worked.
Somehow I could access my backend (both folders with similar wordpress content and database) and I extracted the content, menu, settings for every page/article/plugin. Than I used my fresh install again and put the content, settings, images, … in it manually.
Hard work but this was the only option I had.