Corrupt RSS feed – what did I do wrong?

you have to fix the errors

thanks! But where do i remove the junk mentioned here:
“XML parsing error: <unknown>:580:0: junk after document element”?
I cant find any xml file in my wordpress directory. Im a complete beginner at wordpress, i dont even know where to look.
I really appreciate the help.

Found the solution!
Because i integrated wordpress into my own webpage somehow the rss feed showed the html of my webpage as well,which corrupted the feed. You have to insert <?php die; ?> at the end of the feed files…..
solution here:
https://www.ads-software.com/support/topic/251400