Hi,
First, if you open again the translation popup, do you still see your changes ?
And second, if you go in the Languages tab of the HikaShop configuration and edit your language file, on the right side of the page, you'll see your translation overrides, which should normally contain the translations you've added in the popups. Do you see them there ?
Finally, when you access the page on your frontend with the "debug language" setting of the Joomla configuration activated, you'll see an extra area at the bottom of the page with information about the translation files. It should tell you if it foudn any issue with the parsing of some of the translation files, including the override one. I would recommend you to check that. If Joomla found an issue when parsing the translation override file, it will be written there the line numbers where it found problems in that file. That will help understand what went wrong.