Hi! I am learning english English. Can you correct it? Thanks.

Have you read the book that I gave you last month?
Is he writing his test? Yes He has been writing it since I arrived.
How many children do you have?
What work did you have after Tou had finished University? *
Have you ever seen the Northern Lights?
He lived in London for 3 years. He had studied there, before he understood that he don't **want to be a scientist.

* What was your job after you finished University? (Here in the US, we say "graduated college" or "finished school" as opposed to "finished University".)

** "didn't" woud be the correct usage here, at least in most places. In the American South, which is where I live, it is pretty common to hear someone say "He don't want that" or even more convoluted structures like "I ain't been wanting that", though. But it's not standard, so keep that in mind. I feel like more people you encounter will feel it is incorrect than will think it correct.

Hi! I am learning english English. Can you correct it? Thanks.

Have you read the book that I gave you last month?
Is he writing his test? Yes, He has been writing it since, when I came here.
How many children do you have?
What work did you have, after Tou had finished University?
Have you ever seen the Northern Lights?
He lived in London for 3 years. He had studied there, before he understood that he don't want to be a scientist.