Today one of my friends is receive so sad.

-> Today one of my friend is so sad.

Because one of my classmates is throw the milk to my friend's clothes.

-> Because one of my classmates throw  the milk to my friend's clothes.

We know that true but the one of my classmates is escape away because we know that true later.

-> We know the truth but one of my classmate escape away  because we know it a little later. 

Then the friend was crying.

-> Then my friend is crying