Regarding those you should be able to translate all front office lines in Localizations->Translations->Front Office. There you translate the majority of well coded plugins, errors, themes, etc.
Regarding the browse button I've disabled file uploads but I believe it's text is displayed based on the customer's browser localization settings. If I'm wrong and this is not the case you should also be able to find a string with 'browse' in the same location above.
Best regards,