I know about Loco translate and have been using it for over a year.
However, I can’t find that particular string on the theme and wc plugin files. That’s why I wanted to ask you, as you wrote the theme and you might know where that string comes from. If you tell me whether that string is part of your theme or a plugin that supports the theme, I’ll go into that .po file on Loco Translate and do the translation.
All the strings related to product functions (add to cart, checkout, cart) goes from WooCommerce plugin. So navigate to Loco http://prntscr.com/js7d9t choose WooCommerce > chose the language and insert the string into the search.
If you still cannot find and translate please provide your site admin access we shall check the settings.
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