Not all Dual Audio files are created equal. If you are hunting for Season 1 in Hindi ORG and English, keep an eye out for these specifications in the file name or NFO (info file):
"See?" Robin said. "Dual audio. The original Japanese and a Hindi dub. But look at the label." One Piece - Season 1 Dual Audio -Hindi ORG EN...
Once you find the correct file, you need a proper media player to switch audio tracks. Not all Dual Audio files are created equal