Why is "This chapter is long and difficult" not correct?
This chapter is long and difficult - הפרק הזה ארוך וקשה, זה הפרק ארוך וקשה. Long and difficult here are adjectives describing פרק, and זה is a pronoun and the subject of this sentence.
Native English speakers would say "This is a long, hard chapter" not "long and hard".
Eh, I could see it either way: "It was a long and difficult chapter of his life". And I would probably only say "long, hard" if it was innuendo.
Is it קשֶה (qashe) for male and קשָה (qasha) for female?
Vivek, yes, and the words are spelled the same and only differentiated with niqqud.