Hello @nelson.garcia,
Most of the strings in rtMedia are translation ready. Please, once make sure you have added a proper translation in Portuguese language file for that particular strings.
The name of the file of translation ready strings for rtMedia plugin is buddypress-media.po . It is located at this path : wp-content/plugins/buddypress-media/language
Kindly, let me know if you don't find the strings in the mentioned .po file and still face the same issue.
Thanks.