Hi,
I don't see how this is related to HikaShop.
HikaShop displays itself in the current language.
If you change the current language of the page with the Joomla language switcher, it's joomla which might redirect you to another menu item if the current menu item is set for only one language. So you should look more at how you configured your menu items and the language restrictions you put on them and the other language menu items that you associated with them, etc.
I would personally recommend not to restrict menus to different languages and instead use Falang to translate your menu items. It's a lot easier to handle language switches if you have extensions with several pages per menu item like HikaShop can have.