I selected rhe first answer أستاذي جورج ممتع
This is also correct in meaning, not sure why they said it was wrong
to what i know, here in Duolingo they associated the word أستاذ with Professor only. This word has other uses in daily life and can mean teacher as well but, well, this is Duolingo.
I did معلمي جورج مرح and it was incorrect. Is that just Duo or is it actually wrong?
actually your answer is more "reasonable" than Duolingo's
your answer is correct. It's just Duolingo.