How to change Chinese google to English on iPhone 4s?

Hi, I just bought a iPhone 4s from Craigslist, and it was all in Chinese characters. I changed the language already, but when I search in the google bar in safari, it takes me to Chinese google. How do I fix this? Also, when I'm in the App Store, it says I'm logged on to my account, but when I tried to update my Facebook app, it told me to enter my password for the previous owners apple ID. 1 more problem I'm having, is when I try to download some apps, it says something like "incompatible with Canada App Store, must switch to Chinese App Store." Please help.

I think you should restore the iPhone through iTunes.