Duolingo does not focus on vocabulary.
If any one is interested to learn english from hindi them join my group club code TJ82UG. It will also improve your Hindi if you are an english speaker. Duolingo should also include more words and their meanings . I also found some mistakes in translation by duo lingo.
It is an app on Google play store to learn english go there and install it
If you find errors, do Report them. These courses are made by volunteers, and they are doing it on their own time. The corrections might take some time to be added.