I think Japanese people don't use you for friends and you for polite speech, but you must know better as you are studying the language in school.
We Bulgarians also have the 2 "you", but I'm not really that far into Japanese ... learning it by myself, to know if they even have the 2 forms in the language.
I thought you are always supposed to be polite in Japan, unless you want to deliberately offend someone.

Best way for me is to move to Japan and speak with a Japanese person about that