[Theme: Mystile] Place pictures next to each other

Hi there,

I try to show three pictures in a line, next to each other, but it doesn’t work. Altough it looks quiet right in the editor, the result isn’t right.

How can I place three pictures in a row?

You can see the actual site here: https://zabird.de/ueber-uns/

Thanks a lot in advance, surely it is really easy and I just don’t get it…