“Are you sure you want to discard your video message?” is translated as “Deseja mesmo interromper a gravação e descartar sua mensagem de vídeo?”. This translation conveys additional information that is not presented in the original question; it means “Do you really want to stop recording and discard your video message?”. A faithful translation could be “Tem certeza de que deseja descartar sua mensagem de vídeo?”.