It's Raining Cats and Dogs.

When I was about fourteen (14) I took (made) a trip to England. I was there with other Italian guys of my own age and we were supposed to take a course in (of) English. The first day in that college,  we had to take an exam in order to establish our level of English and to be divided into (in) different classes.
We arrived there (in this place) early in the morning, in time for (while) the test (would have been) in the afternoon. During the morning we had our (the) first meeting with the strange (and lovely) UK weather: (of the UK:) after an hour or two it suddenly started to rain. My friends and I took refuge nearby the school and there we met some native people who were waiting for the rain to pass. (away.) Those three people remarked (told us): "see, it's raining cats and dogs!" and I thought that no animals were falling from the sky. (And) Then they said "Remember this for your test."
In fact, when we finally took the exam we found that those three people were our future teachers of English and that there was a question about some idioms with "it's raining cats and dogs" as the answer.
I've never forgotten this funny episode.

Quite an amusing story. Your English is very good. It is usual to write the title with initial capitals. We would write numbers in full in English; we say 'took a trip' or 'travelled to'; 'divided into'; as you are talking about a place away from you, we would refer to it as 'there' or 'that place'. 

It's raining cats and dogs.

When I was about 14 I made took a trip to England. I was there went with some other Italian guys (I think it sounds better to say 'Italians' instead of 'Italian guys' which is rather informal) of my own age and we were supposed to take an English course of English. On the first day in that college we had to take an exam in order to establish our level of English and to so that we could be divided into different classes.
We arrived in this place early in the morning for while the test would have been in the afternoon. During the morning we had the first meeting our first encounter with the strange (and lovely) weather of the UK (this arrangement with 'of the...' is not natural in English, better to say 'strange (and lovely) British weather): after an hour or two it suddenly started to rain. My friends and I took refuge nearby the school and there we met some native English people who were waiting for the rain to pass away. Those three people They told us: "See, it's raining cats and dogs!" I thought it was strange as that no animals were falling from the sky. And then they said "Remember this for your test."
In fact when we finally took the exam we found that those three people were our future English teachers, of English and that there was a question about some idioms with which had "it's raining cats and dogs" as the answer.
I've never forgotten this funny episode.