Hello,
By updating/upgrading HikaShop version you won't loose any information. It will just update the files and add new columns in the database if required.
Your views overrides (via "Hikashop->Display->Views"), css overrides, language, configuration, orders, products will stay intact.
But careful if you have modified directly an HikaShop file and you didn't use the backend interface for that. Because you could loose your modifications.
Making a backup is always a good security.
Note that You'll find more information about it through the documentation :
www.hikashop.com/support/documentation/5...-install.html#update