Why does the “image Block full width” not work?

I installed the demo page “gutenberg styling” and even here where i havent changed anything, the images are all normal width, nothing wider than the text. You can see it here: http://lenas-fotografie.de/gutenberg-styling/
I am referring to “image Block wide width” and “image block full width”. Same goes for “Cover image block” though. 
If you look at the demo page https://hellorose.helloyoudemos.com/gutenberg-styling/ it is displayed the way i want it. 

What am i doing wrong? :S
 
Thank you in advance!