Hi @danar,
In detailed page of an Event article, it will show the Introtext of article in blockquote style, then the full text of article.
As I can see from your attached screenshot, there is only one content paragraph, Joomla will consider it as both Introtext and Full text of article so when you view the detailed page, it will show both.
The normal behavior when creating content for an article is that you will create intro text and full text which can be separated by the ‘Readmore’ button.
In case that you don’t want to show the intro text in detailed page, you can access backend settings of menu item this page belongs to > check the Options tab and set the parameter ‘Show Intro Text’ to ‘Hide’ : http://prntscr.com/fghnzd
Regards
