Are these sentences correct? (Cover letter)

I've been studying at Fake Lesson Center, a school that ensures students get proper training for the ENS.

"My two years of associating university and preparatory classes have helped/made? me (to?) become a more hardworking person."

My two years of attending university and preparatory classes have helped me become a more hardworking person.
Two years of attending university and preparatory classes have made me a hardworking person. (Slightly more natural)
Two years of attending university and preparatory classes have taught me the value of hard work. (Better nuance)
Two years of attending university and preparatory classes have broadened my knowledge and taught me the value of hard work.  

"This is for me the perfect opportunity of studying what I'm interested in"

This is a perfect opportunity for me to study what I'm interested in. (More natural than your two options)