http://www.perfect-english-grammar.com/present-continuous.html

Here is how we make the positive:

Positive	Positive Short Form
I am sleeping	I'm sleeping
you are sleeping	you're sleeping
he is sleeping	he's sleeping
she is sleeping	she's sleeping
it is sleeping	it's sleeping
we are sleeping	we're sleeping
they are sleeping	they're sleeping

We can make the negative by adding 'not':

Negative	Negative Short Form
I am not sleeping	I'm not sleeping
you are not playing	you aren't playing
he is not reading	he isn't reading
she is not working	she isn't working
it is not raining	it isn't raining
we are not cooking	we aren't cooking
they are not listening	they aren't listening

Practise making the positive and the negative forms (exercise 1) Practise making the positive and the negative forms (exercise 2)

Questions are also really, really easy. Just like we made the question with 'be' in the present simple, here we also put 'am', 'is', or 'are' before the subject to make a 'yes / no' question:

Yes / No Questions
am I eating chocolate ?
are you studying now ?
is he working ?
is she doing her homework ?
is it raining ?
are we meeting at six ?
are they coming ?

For 'wh' questions, just put the question word at the front:

Wh Questions
Why am I eating chocolate ?
What are you studying now ?
When is he working ?
What is she doing ?
Why is it raining ?
Who are we meeting ?
How are they travelling ?