order of opening the image

Hi,

The next/previous buttons on the images display area of the product page and displayed using FontAwesome. So they are not images.
You would have to hide them with a color:transparent CSS command, and then use a background-image to add your own image instead.
I can see you've added instead a display:none CSS command. That's fine too. However, I can see you've added it directly to the hikashop.css file. I would recommend you copy/paste the whole CSS command to the "style for the frontend" setting of the HikaShop configuration, or in the custom CSS file of your template. That way, you won't loose your change each time you update your HikaShop.
You can read more about this here:
www.hikashop.com/support/documentation/1...ize-the-display.html

Merry Christmas !