Hi there,
Regarding,
> on a mobile device sliding marketplace photos moves the menu bar as well
I'm unable to replicate the first issue. Check out the attached screenshot.
However, about the second issue,
> also the next button does not show the next photo but instead changes to the last photo
It seems like there is a conflict with the Pixel swiper slider script. There are some errors on the console and I'm able to replicate this issue locally. I've logged this to our developer to fix it.
Anyway, can you help me test with Protostar template and let us whether you're able to replicate this issue.
Thanks.