I am a man 我是一个男人（wǒ shì yí gè nán rén)
I am not a woman 我不是一个女人 （wǒ bú shì yí gè nǚ rén)
He is a man 他是一个男人（tā shì yí gè nán rén)
He is not a woman 他不是一个女人（tā bú shì yí gè nǚ rén)
She is a woman 她是一个女人（tā shì yí gè nǚ rén)
She is not a man 她不是一个男人（tā bú shì yí gè nán rén)
it is a cat 它是一只猫(tā shì yì zhī māo)
it is not a dog 它不是一只狗 (tā bú shì yì zhī gǒu)

Wish it can help you. :)

this is a book ,zhè shì yì běn shū,这是一本书
that is a dog，nà shì yì zhī gǒu,那是一只狗
these are books，zhè xiē shì shū,这些是书
those are dogs，nà xiē shì gǒu,那些是狗

You can not learn them all at one time.Just remember them when you come across with them. If you have any questions,you can contact me. :)

There is no other way,learn it one by one,there isn't much.

Yes,you are right.

yí gè means one/a/an

for example, an apple=yí gè píng guǒ

But keep one thing in mind,we use different classifier measure word for different noun.

For example, one desk=yì zhāng zhuō zi

That's the difference.