Shopin(with J2Store inside) supports multilingual. You can build a store with different languages. And it's a must-have feature in your site if you are running your business in different countries. To build a multilingual Joomla shopin site, you need to know how to translate CMS, template and used extensions. 

Process of translation is quite easy:

1. Install 2nd language for Joomla!
2. Configure that language
3. If you need set multilanguage feature in Joomla. 
4. Download and install translation for J2Store from the developer website: www.j2store.org/translations.html
5. Translate selected phrases from that file: language\en-GB\en-GB.tpl_shaper_shopin.ini

SHOPIN_ACCOUNT="Account"
COM_USERS_LOGIN_TITLE="Log In"
COM_USERS_LOGIN_USERNAME="Username"
COM_USERS_FORGOT_PASSWORD="Forgot your password?"
COM_USERS_LOGIN_DONT_HAVE_AN_ACCOUNT="Don’t have an account?"
COM_USERS_NEW_ACCOUNT="Create a new account"
HELIX_LOGIN = "Login Here"
HELIX_ALREADY_ACCOUNT = "Already have an account?"
MY_ACCOUNT="My Account"
COM_USERS_REGISTRATION_TITLE="Create An Account"
COM_USERS_REGISTRATION_SUBTITLE="Sign Up"
HELIX_REGISTRATION="Registration Page"

For example create: xx-XX\xx-XX.tpl_shaper_shopin.ini
Where xx-XX  - is your 2nd language code.