Need help with my diary

[kwfine]

Dear Alan,

I am writing a diary.
Could you tell me whether there are any mistakes in the following sentences please?

He was a graduate of ABC University in 2011.
It has been 3 years since then from 2011.( 2014 - 2011 = 3 )
Now he wants to go to a university to study another course.

Thank you.

Kitty

[Alan]

#2: -->3 years have passed since then (2011).