أختي دائما مشغولة .
...is not a typo, is it? That's what duo says. I'm a native speaker and it sounds completely natural to me. Or is it actually incorrect?
In arabic, the adjectives comes last most of the time. Eg عندها جاكيت جميل The literal translation is "she has jacket pretty." That's why we say بيت كبير (house big) instead of كبير بيت
The correct version is اختي دائماً مشغولة with a ة. Duo accepted it, but told me I have a typo and corrected it to مشغول. This is incorrect. The subject is "my sister", therefore "busy" must be in feminine form.
Please fix.
To be clear, they allow دائماً to come either before or after مشغولة, however they use masculine form if you put دائما first. It should still be in feminine form regardless of its position in the sentence.