"Sopravvalutare" means "overrate" as opposite of "underrate"(sottovalutare)and is usually used when talking about a person. -Non sopravvalutare Michele: non sei meno intelligente di lui (Don't overestimate Michele, he's no smarter than you are). "Sovrastimare" is kind of the same thing, but referred to material goods (lands, properties, budgets, etc.)

"Qual è", you don't need to put an apostrophe :)