Hi,
Go in the Languages tab of the HikaShop configuration and edit your language file. Is that text translated in your language file or not ?
If no, then you can translate it yourself.
If yes, then it means that there is an error in the translation file you're using and in that case the system is default to the English translation. Turn on the "debug language" option of the Joomla configuration and check at the bottom of the checkout page. You should debug debug data of the language files parsing which will tell you on which line of which file there is an error so that you can correct them. Once the parsing of the HikaShop translation file is valid, you should not have the issue anymore.