I looked up my problem in the support forum. It seems that others have had the same issue. Yet the custom CSS that was proposed in their case did not work on my site.
Here’s the issue: The pictures on my webpage are integrated with the Visual Editor of the Black Studio TinyMCE Widget. On the desktop, they look good but on the mobile version, they have a weird margin that I cannot fix (see pictures below). My URL is: www.sonjakoeppel.ch
Can you please give me a hint or send me a few lines of code? Thank you so much!