gallery shows images in another gallery that is in the same page

Does that theme provide the lightbox feature or some gallery plugin?

@imoptimal yes it has gallery feature, but all images from different galleries open in a single lightbox. I want to have multiple lightbox like this plugin

https://www.wonderplugin.com/wordpress-grid-gallery-lightbox/how-to-open-a-different-lightbox-gallery-on-click-each-image-in-a-grid-gallery/

Based on their official documentation I don’t see any option to do something advanced like that.

You should ask their user support, just to be sure. But if there’s indeed no option in the theme, you would need to consider another solution (like the plugin you mentioned).