Special verbs in the Simple Present

1) have as a full verb
affirmative sentence	negative sentence	question
I, we, you, they:
I have a book.	I do not have a book.	Do I have a book?
he, she, it:
He has a book.	He does not have a book.	Does he have a book?

2) be as a full verb
affirmative sentence	negative sentence	question
I am from Britain.	I am not from Britain.	Am I from Britain?
he, she, it:
He is from Britain.	He is not from Britain.	Is he from Britain?
we, you, they:
We are from Britain.	We are not from Britain.	Are we from Britain?

We often use the short forms with this verb.

3) do as a full verb
affirmative sentence	negative sentence	question
I, we, you, they:
I do an exercise.	I do not do an exercise.	Do I do an exercise?
he, she, it:
He does an exercise.	He does not do an exercise.	Does he do an exercise?

4) modal auxiliaries can, could, may, must, need, will etc.
affirmative sentence	negative sentence	question
every time regardless the subject (I, he, she, it, we, you, they):
I can play tennis.	I cannot play tennis.	Can I play tennis?

NOTE:
We can subtitute don't (can't) for do not (cannot).

Modals have the same form every time regardless the subject. We do not add an -s to the infinitive.