NegationsRemember AGAIN:
The verb 'to be' is a special one. So are 'can' and 'have got'.
If it's the first verb in the sentence: just add not.
She sings very beautiful. She doesn't sing very beautiful.
We are at home. We aren't at home.
They can swim very well. They can't swim very well.
They cannot swim very well.
He has got a dog. He hasn't got a dog.
But...
He has a dog. He doesn't have a dog.