Portfolio: bug in Safari 10

Hi community,
these days I started my first web project using Gutenberg. https://homepage-4-you.net/andersicht There is one thing that I do not understand: When using a gallery (4 images in a line) everything works well in all browsers except Safari 10. But in Safari 11 I could not see any problems.

As far as I know Safari 10 and Safari 11 both use modern web standards. And the additional CSS I use in the classes of that area is really simple. So I cannot imagine that the problem is located in my css. Nevertheless I post it:

.page-id-130 .galerie-schmal-ueberschrift {width: 70%; margin: 0 0 0 30%; padding: 20px 20px 0 20px; background: #FFDA7A !important; font-size: 34px !important; font-weight: bold;}
.page-id-130 .galerie-schmal-fliesstext {width: 70%; margin: 0 0 0 30%; padding: 0 20px 20px 20px; background: #FFDA7A !important; }
.page-id-130 .galerie-schmal {width: 70%; margin: -1.5em 0 0 30%; padding: 20px; background: #FFDA7A !important;}

So: Where the problem might be located? Is it a bug of Gutenberg when using the galleries-block? I kindly ask for any useful advice, since I have no idea where to start searching. ??

Thank you!
Raphael

The page I need help with: [log in to see the link]