"Ich spiele die Mutter."
There is nothing wrong with the English sentence. Replace "the mother" with almost anything else, and any actor could spew forth this sentence while being interviewed before the release of a movie.
- "What's your role in the new movie?"
- "I play the mother/father/brother/teacher/villain/hero/sidekick/captain/coach/etc."
A child could utter it to his/her parents:
- "What's your role in your school play?"
- "I play the horse/donkey/tree/sun/pineapple/fish/tectonic plates/atom/etc."
Remove "the", and an athlete would say:
"I play left wing/nets/tender/center/defence/etc."
Putting aside the fact that all the sentences being put forth by Duolingo are simply to help you learn vocabulary and grammar, these so-called "nonsense" or "abstract" sentences are just as valuable in the learning experience as the mundane ones like "The apple is round". I'd argue that these sentences are actually more useful in some cases, especially in daily conversations or when watching television or movies.
It isn't a British thing. If Carol Ann Susi told you that she is on "The Big Bang Theory", you'd probably say that you don't recognize her, followed by "Who do you play". She would reply "I play Howard's mother". If she was the only mother on the show, she would say "I play the mother."
- "Hey, Chris Pine, what's your role in the new Star Trek movie?"
- "I play the captain."
Manuel Neuer would say "I play nets" or "I play keeper" if asked what he does for a living.
The so-called "nonsense" sentences that you may encounter on Duolingo are examples of sentences you will encounter in daily life, whether in discussions, on T.V. or in songs.
I think...that not all sentences need to have a meaning, quite frankly I see a lot of them that make no sense, but that's not the point, the point is that you learn the words and their meanings. Maybe the setences will be more in the spirit of the language as the lessons get harder.