Can someone tell me how one would say "Hooray!!" in Italian?
Grazie per il suo aiuto.

Si dice Hurra' !
Hip Hip Hurra !
In reality is the italianized version of the English / American word

has anyone heard of kalle stille

The Italian letter h at the beginning of a word is silent; it is used to distinguish ho, hai, ha, hanno
(present indicative of avere, 'to have') from o ('or'), ai ('to the'), a ('to'), anno ('year') but there
is no difference in the pronunciation of such words. H is also used in combinations with other letters .
In foreign loanwords, the h is still silent: "hovercraft" /ˈɔverkraft/.
uh-RAH!

A proposito, the letter h is also silent in Spanish.