Student or Learner
1) After i visit Paris, it completely change my perception towards the place.
2) Paris is completely the opposite of my preconceived notion about it.
3) My stereotype thought about them have reduced after visiting the place.
1) Since visiting Paris, my perception of the place has completely changed.
1) After I visited Paris, my perception of the place changed completely.
2) Paris is the complete opposite of the preconceived notion I had about it.
3) The sterotypes which I thought about them (the French) have changed since my visit.
I'm sure there are many other ways to word your sentences, but these are a few examples. I hope they help.