Tam and Cam (A Vietnamese Fairy Tale)

Once upon a time, when the rain forest covered most of the lands and people were still afraid of wild beasts, there lived a family of three on the edge of the forest.  Tam was a kind and gentle girl.  She has a younger stepsister named Cam who was very spoilt and  Cam's mother was mean to Tam.  She would yelled at her for nothing and would even whipped her at the slightest excuse.  Day in day out, neighbours would hear,

"Tam! Why is there dust at the entrance of the door?"

"Tam! You good for nothing lazy bones!  Why are you nodding off when your work is not done yet!"

If the stepmother did not yell at Tam it is because she was asleep!

One day, the stepmother called out to them,

"The weather is perfect, neither too hot nor too cold."

With her outstretched arms and fluttering her eyelids she purred,

"I feel there are many fish jumping around in the river...  hmmm... Go and take some fish nets with you and bring back some fish as special treat for me."

The sisters obeyed her wishes and ran to the river quickly.  There were birds flying in the trees, lazy clouds seemed to be nodding off in the sky.  A perfect day to escape from the heat of the sun.  Soon they reached the river. 

Tam was busily casting the net into the river to catch the fish while Cam just laid on the grass, singing merrily and soon she fell asleep.  When evening came, Tam woke Cam up.  As she opened her eyes slowly, she realized that it was too late to catch any fish.

"Oh dear, mother will kill me!"

As she cried, she espied Tam's basketful of fish.  A wicked thought was born in her mind.

"Those fish could be all mine!  No!  It is mine!  It hast to be mine!"

Cam said smiling at her stepsister,

"Oh no!  Just look at you dear sister!  Your clothes are dirty and smelly.  Mother will surely punish you!  Better go and wash up.  Don't worry, I will look after your fish."

"Really?  Please do, Cam."

And that, Tam ran quickly to the river to wash the mud off her body.  What a great opportunity for Cam to act out her evil thoughts.  She quickly poured all the fish into her own basket and ran home quickly; leaving Tam alone with her empty basket.

I hope that that's not end of the story!  If so then you are not writing a very good story.  If NOT, then it is a very good time to stop and continue the next time.  This is called a cliff hanger.  You must compare what we wrote.  Not only are there grammar mistakes but logical ones as well.  For example, the way you wrote in the last line, It was Cam who was left behind with her empty basket.  Don't use too many pronouns together in one sentence when the reader could not understand for the context the two different "shes" you are referring to.  For example, see 1 in your original text.

Once upon a time, when the rainy forest was still covering most of the wild landscape and the wild animals were still a scare for people, there was a three- member family living in a countryside.They were an older sister named Tam who was so kind and quite, a stubborn youngest and Tam's stepmorther, or Cam's mother, who was always so talkative. Day after day, their neighbourhood just heard the cry of Tam when her stepmother had been yelling at and whipped her for some tiny reasons as "Why don't you let the dust covering the door,Tam?","Why do you always nod off when you haven't finished your mission?". If one day she couldn't found out any reason to punish her, she could be falling asleep tenderly. 1 This sentence is unclear and ambiguous.  Who is sleeping, the stepmother or Tam?  So in my correction, I assumed it was the stepmother and so I wrote differently.

Once day, the stepmother called them and odered:
- "The sky is so pure and cool, not too shiny or hot", she opened her arms and closed her eyes and continued:" I can feel many flocks of fish hanging out slowly outside in the river. Mmm.. Mmm... So you all can take the fish net and go to the riverside. Someone who can collect more fish will receive my special gift". Then, two girls followed her mother's oder and run out quickly. The flocks of birds on the tree jumped from the branch to other, the lazy clouds seemed like nodding off in the sky...They all wanted to hide the heat from the sun burning anything underneath. A short time later, they were at the riverside. Tam hurried up to put the net into the river while her younger sister was lying on the grass and sang la la la and falling into sleep. In the evening, Tam rocked Cam and waked her up. Opening slowly her lazy eyes, she realised it was too late to catch the fish.
-"Oh my god, you had killed me,sister !".She shouted out aloud and then she cried.
Looking at Tam's basket which was full of fish, there was a dark thought appearing in her mind: "Why the fish in her basket can be mine? No, It's mine.It has to be mine." Then,she steped to and smiled at her sister.
-Oh,no sister, you see that your cloth is so dirty and smell. Mother will punish you unless you have to take bath and wash your cloth now. Don't mind about your fish, I will help you keeping it"
-Really??? So please keep it, Cam.
After that, Tam run to the river quickly and washed all the mud out of her body. That was like an opportunity for Cam to act her crime. She hurried up to pour all the fish from Tam's basket to hers. Then, she run back home and leave Cam alone with her empty basket.

Tam and Cam (A Vietnamese fairy tale)

            Once upon a time, when the rainy forest was still covering most of the wild landscape and the wild animals were still scared of people, there was a three-member family living in a countryside. There was an older sister named Tam who was so kind and quiet, a stubborn younger sister, Cam, and Tam's stepmother, Cam's mother, who was always so talkative. Day after day, their neighborhood just heard the cry of Tam when her stepmother had been yelling at her and whipping her for any tiny reason as "Why don't you clean the dust covering the door,Tam?","Why do you always nod off when you haven't finished your work?" If, one day her stepmother couldn't find any reason to punish her,  Tam could fall asleep tenderly.
            One day, the stepmother called the girls and ordered, "The sky is so pure and cool, not too shiny or hot." She opened her arms, closed her eyes and continued," I can feel many schools of fish swimming slowly in the river. Mmm. Mmm.  Take the fish net and go to the riverside. The one who can collect the most fish will receive my special gift."

            The two girls followed the mother's order and ran out quickly. The flocks of birds in the trees jumped from one branch to another and the lazy clouds seemed to be nodding off in the sky. They all wanted to hide from the heat of the sun burning anything beneath. A short time later, they were at the riverside. Tam hurried to put the net into the river while her younger sister laid on the grass and sang "la la la".  Soon, she fell sleep. In the evening, Tam rocked Cam and woke her up. Slowly opening her lazy eyes, Cam realized it was too late to catch any fish.
            "Oh my god, you had killed me, sister!" She shouted aloud and began to cry.
Looking at Tam's basket which was full of fish, a dark thought appeared in her mind. “The fish in her basket can be mine. Yes, they are mine. They have to be mine." Then she stepped forward and smiled at her sister.
            “Oh no, sister, your clothes are so dirty and they stink. Mother will punish you unless you take a bath and wash your clothes right now. Don't worry about your fish, I will keep them safe for you."
            “Really? Yes, please keep them for me, Cam.”
            After that, Tam quickly ran to the river and washed all the mud off her body. This was the opportunity for Cam to commit  her crime. She hurriedly poured all the fish from Tam's basket into hers. Then she ran back home and left Tam alone with her empty basket.