"The picture is too small"
You have widths set to 650, that's very big actually. On some screens, there would not even be space for a second gallery beside.
"is there even a way to code captionposition"
Sure there is. But you have to be specific in what you want.
Anyway, yes two (or even more) galleries side by side are possible, technically. There are several ways to do this, for example using CSS flexbox or grid, or also just divs with a fixed width. It could even be done with a table (which is a terrible idea, don't do it).
Still, I don't think it makes really sense.
Maybe you should try to explain in more detail what exactly you want to achieve with this and how it should work and look, and also link to the page so we get a better impression.