I mean, normal actions of PhotoSwipe is to scroll horizontally and to close after vertical swipe. I would like to switch actions so it scrolls vertically and closes after horizontal swipe.
Does anyone know how to do that?
You'll likely need to download the source from the GitHub repo and make the changes yourself.
Looking at the _panOrMoveMainScroll method in src/js/gestures.js, it appears that the panning logic is only present for horizontal gestures _direction === 'h' && axis === 'x', whereas the mainScroll is present for vertical gestures.
If you think this is useful enough to warrant the development effort, I'd recommend taking the latest branch and adding a default option in core.js that allows the directions to be toggled and issuing a pull request to the original repository. This way future users can benefit from your effort and simply set a property to switch the directions.