Okay. I found it how to do it. Sorry again. Now it is deleted.

I don't know. I thought I deleted it. I am sorry, I did'nt do it on purpose. How can I delete it now (afterwards) in JOSM ?

I saw it to late, that I shouldn't delete the relation. I am sorry, but it happened by chance. So that there is no gap, I made a new one. And updated it on the page.