Hello, fellas. How long have you been learning English? In this session we will learn how to ask about and express length of time.
According to Betty Schrampfer Azar, a question about length of time is started by how long.
1) How long did you sleep last night?
2) How long will they stay in New York?
How long can be replaced by how many + minutes/hours/days/weeks/months/years.
How many weeks will they stay in New York?
On the other hand, length of time can be expressed by this formula:
It + Take + (Someone) + Length of Time + Infinitive
(Infinitive = to + the simple form of a verb)
1) It takes 90 minutes to play football.
2) It took Mary two months to write her book.
Betty Schrampfer Azar, Fundamentals of English Grammar: Third Edition