Remember: the adjective has a suffix that denotes the gender in Italian. Therefore, if you say "nice" to a boy you use "carino", otherwise to a girl you use "carina".
Pay attention: "to know" in Italian can be translated as "conoscere" or "sapere", but they are used in different contexts. "Conoscere" is mostly used in relation to a place, a person, while "sapere" is related to a fact.