how can I add a "next" button in product gallery

Hello,
I have this issue with opening a pop-up image of product pic, but without posibillity to go to the next one.
see: http://www.xcape-room.ro/marui-1911-strike-warrior

can you point me in the right direction to solve this issue?
Thanks

If I understand you correct - and after a quick look at this page, you don't want to have the zoom function?
Instead a function/library where you can move left and rigth?

Then, either use another template or another library.

it's correct
can you guide me how to change library?