Changing to another supported language should be jsut like you described. However, if there is no translation for the selected language, it will fallback on English. You can find if your language is supported by looking at the files in <efcBinPath>\App_GLobalResources\. Where <ecfBinPath> is where you installed the Commerce Manager site.
In the default installation we only support English, Danish, Finnish, Norwegian, Swedish, Dutch and Japanese.
Have you selected the languages in the top category of your catalog?
Be aware that you make sure that multiple languages are selected, because the multiple selection is not clearly shown.
I'm trying to change the language of EPiServer Commerce but no luck !
I managed to change the language of the CMS BUT not for the EPiServer Commerce - How to do so ?
EPiServer Commerce Dashboard Home has an option called "Change Language", and on clicking of it, it gives 7 languages, and when I select any of them, and press OK. Nothing gets changed.... I still see "Customer Management" , "Catalog Management", "Order Management"...etc all in english .... So, could you please guide me how to change the language ?