He is cooking?
Is he cooking?
He is look after a dog.
He is lookING after a dog.
A police officer is growing vegetables.
A FARMER is growing vegetables.
They serving drinks
They ARE serving drinks.
A waiter is cooking.
A CHEF / COOK is cooking. A waiter is SERVING food and drinks.
You mustn't follow the rules.
You MUST follow the rules.
I'm writeing
writing
He's studing.
studying
What is you doing? I'm having breakfast.
What ARE you doing?
A mechanic is fix a car now.
A mechanic is fixING a car now.
You must drop litter.
You MUSTN'T drop litter.
You're swiming.
swimming