Present Continuous :

( Am – is – are ) + V ( ing )
Ex : Sami is reading a book
2- I am writing the lesson .
3- They are wearing jackets .

Negative :
1- Sami is reading a book .
Sami isn't reading a book.

2- I am writing the lesson .
I am not writing the lesson .

3- They are wearing jackets .
They aren't wearing jackets