I found the Joomla Inhalt option. Blog output is now shown.

Still, is it possible to show the articles via ShortCode and with the title displayed mandatory?

Yes, therefore you have to edit the shortcode parameters for the showcase in the single article.
All parameters can be found in the link
bdthemes.com/support/knowledge/details/2...ode%20attribute.html

Can you give me the parameter. I cannot find it. Tried almost every parameter of the Showcase object, but i still have to hover....

Hello,
1.) I dont know if this is possible
2.) Here are shortcode ( showcase) samples
bdthemes.net/demo/joomla/shortcode/en/shortcodes/showcase.html

3.) Add a new shortcode - Select showcase - And now you see which parameter you can chose