なかなか-(Vないform)ない
Usage
なかなか with the negative form of a verb means "not easily" or "not readily". Usually, it is used when something desirable doesn't happen easily or when something that is supposed to happen doesn't happen. Not easily; not readily; difficult to -; slow to; to refuse to
Examples
バスがなかなか来ない。授業に遅れてしまいそうだ。困ったなあ。
The bus is taking quite a while to arrive. I might be late for class. This is troubling.
一年生の時は漢字がなかなか覚えられませんでしたが、今は、あまり時間をかけずに覚えられます。
When I was a first-year student, I had a hard time remembering kanji, but now I can remember them without spending too much time.