I am not sure about the correctness of these two sentences:It is a very good example why each person should be honest and this experience has changed my mind.
The university was significant part of my life because it has provided me with valuable experience and has changed my mind.
I concern about coherence of tenses: present simple + present perfect and also past simple + present perfect.
The idiom "changed my mind" means "I thought one thing; now I think another". It's normally used for one specific (often trivial) thing at a time. You always "change your mind" about something.
A: I thought you were having vanilla ice cream?
B: I've changed my mind. I'm having chocolate.
A better way of saying what you want is "it changed my way of thinking / it changed a lot of my ideas / it challenged much of my previous thinking ... "