This is an accepted solution.
Nick here from Shopify. Great question!
There are a few different ways to translate your store language. Although Shopify themes are in English, some themes have more than one language option. These themes include translations of all of the text content in your online store, such as contact information and cart and checkout information. For themes that include multiple languages, you can simply change the theme language. If your theme doesn't have the language that you want, then you can create the translations yourself. Something to remember is that you can only have one active language on your store. You can see more about translating your theme from the help guide Shopify has about it here. It would often depend on the theme you are using in this case though.
If you are using a theme which doesn't have a translate option, the best next way to do this, is via an app from the Shopify App store. There are a few different apps which spring to my mind for this which I feel could be worth looking into. Let's take a look at them below:
Something to note is that the apps don't translate the content for you.
I believe the same concept would apply for marketing as you would create those yourself as well as the notifications and Shopify Emails. I hope this helps and don't hesitate to ask if you have any other questions!