1 My bad memory power.
My main reason is that my preparation / review is not enough.
2 When I remember one word, you need to memorize some pattern changes.
It has regularity but I hardly remember that rule.
3 Mr. Junzo Kashiyama who studied Russian at the Osaka Trade Language School said that “There are only 70 people at the time of admission and only 7 at the time of graduation.”
It is difficult and it seems to be frustrated.
It only memorizes a lot, but that is difficult.
I decided to learn Russian, so I will try hard without giving up on it.