- " Shati" has only one form so, it means both - plural or singular. 2. They told I am wrong writing - (....) a shirt- because it should to be - "my shirt" what is wrong.
"I take off my shirt" is more natural English. I'd almost never say "I take off a shirt" or "the shirt".
Right. This problem comes up in other sentences in this level. I've reported it. "The shirt" implies you're undressing someone. Well maybe....