presente simple 

It is used to talk about habitual actions, generic, occurring with some frequency

Affirmativo
They work in an office,
I works in an office

negative
They do not work in an office
I does not work in an office

interrogative
do they work in an office?
does he work in an office?

They work in an office?
yes they do / no they do not

I work in an office?
yes he does / does not have

The form of the present simple infinitive matches except for the third person singular in which is added a / s' /

I / You / We / They It / She / He
eat eats
run runs