If you are selling products internationally, we do recommend you:
Set English as your store default language, and other local languages as Target because English can be understood by most users.
Go to Translation > Language Settings > Visitor's Language Detection > Enable Visitor's langue detection and choose Visitor's country, because not 100% users will use local language in their browsers.
For example, you want to setup Portugese for visitors from Brazil automatically, and English for other visitors, make sure you have Portuguese (Brazil) in Target language list, and choose option "Visitor's country".
Otherwise, if you think your users are from one country only, feel free to set local language as Store default language, and choose Store default language in Language Settings section.
If you need some more helps, please feel free to contact us via live chat or email us at email@example.com