For multi language, There are 4 ways to do multi-language shopify store.
1) multiple stores, by using 2 separated shopify stores. The pros is, you can customise and localize all the sections and email notifications individually. But the cons is you will need to manage the orders and inventory in 2 separated backend and you will need to pay shopify fee for 2 stores.
2) By shopifyninjas bilingual theme. This is once easy manage way for bilingual. But there is only one theme for selection, by choosing this method, the store design, layout will need to follow the theme. And the secure checkout section and email notification are not translatable.
3) By "langify". The pros is 1 single store management. The cons are langify is not able to translate the interface of some 3rd party apps.
4) Google translate widget
One easy way is to install Google translate widget into the site, and the widget will handle all the translation. But since it is a auto translation, there will be no control or customisation can be made to the translation results.
5) By Localize.js