Magento – Magento 2 translate the “You added … to your shopping cart.” line

Ok, so finally got this resolved by creating a new language pack, modified certain template files and cleared all caches:

1. Created a new language pack:
   • created new folder inside app/i18n/< vendor >/xx_xx/
   • created 3 necessary files: language.xml, registration.php, xx_XX.csv according to official guidelines (mind lower and uppercases of folders and files)
   • translated the store front within the csv
   • cleared all the caches within administration
2. As almost all strings were translated except the minicart & checkout items my next steps were:
   • copied each corresponding html file for specific element to my theme_folder/module which started to pull the new translations from my language pack. For example on how i translated mini cart string "Recently added item(s)": i copied the content.html from app/design/frontend/< vendor >/< blank >/Magento_Checkout/web/template/minicart/content.html to my corresponding theme module folder. Doing this the translations from my language package were getting translated.

Those strings that didn't get translated in step 1. and got translated in step 2. by copying the module files to theme folder had the attribute data-bind="i18n.

Reference: Creating a language pack in M2 (official)

You should use double quotes when a translation string already has or needs quotes (for example: attributes for inline translation html elements) - like this:

"If you have questions about your order, you can email us at <a href=""mailto:%store_email">%store_email</a>"","Für Rückfragen stehen wir Ihnen jederzeit gerne zur Verfügung. Sie erreichen uns per E-Mail unter <a href=""mailto:%store_email"">%store_email</a>""