Articles

Today, I learned "Articles" And tomorrow, this topic continue.
I cannot understand them!!!
"a" and "an" are easy to distinguish, but when I need to use them?
And also "the" and "some" !!!!
Why English have such a complicate rule!!!!!
I think Japanese have articles but it doesn't have "a" and "an". Or if it has "a" and "an", we rarely use them in a conversation.
When I say " I saw a dog. The dog has white far and blue eyes." in Japanese, I just say " I saw dog. The dog have white far and blue eye" In Japanese "eye" indicate "eyes". When you want to specify "an eye", you need to say "right eye" or "left eye"
We also do not say "the sun" or "the moon"
We just say "sun" or "moon"

????? I wonder, Japanese articles are more complicate than English one?
Some times necessary to use articles but some times are not.

Anyways, for me, FOR ME it is complicated!!!!
I need to understand them!!! Final test is coming soon!!!
Oh, scary!!!!