Hi,
Please be sure that your HikaShop Spanish is right up to date and contains all required translations.
You can also activate the Joomla language debug mode in order to see if you had some issues with the language files.
As you can see, some elements are translated, like the "add to cart" text.
HikaShop does not load the language files, Joomla does.
So there is nothing special to do in HikaShop because Joomla will load the spanish language file if the current language is the spanish one.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.