Thanks to both of you.
The solution from alexandros worked - the sound now is working. And yes, its another output with the same name which was chosen by default.
I had not considered it as an solution because its realy the same name.
Here the screenshot (in case someone in the future with the same problem finds this):
its a real basic question which I have.
I do not get any audio output.
In an tutorial I have seen that someone marked the checkbox "compute audio" in the main window of PD (first picture) to solve this poblem.
But I do not have this checkbox (second picture). There is only the phrase "Audio aus" (which is German for "Audio off"). But I can not click anything around that phrase. The DSP checkbox I can check and uncheck, but without any audio changes and the phrase "Audio aus" is not changing.
I'm using Pd version 0.52.1.
What can be the problem?