Hey there,
whats the best way to reduce the margin on the right side of the feature headlines here under my menu bar: https://www.adsventure.de/
The class is: feature-headline-front
Maaaany thanks! 
Hello There,
I have checked your site and I could tell that each of the featured headline were enclosed in a 1/4 column. Please edit your page again in Cornerstone and go to the row settings. Enable the Marginless column options and this should reduce the amount of spaces in the right side of the featured headlines.
Hope this helps. Kindly let us know.