5分 The meaing of "oh i see"

1. Oh I see: means I understand, or I get it.
中文：啊，我了解了。
example:
Mr. A: are you a student?
Miss B: No, I'm a teacher. I'm not a student.
Mr. A: Oh I see.

2. Wanna = want to
it's not a proper english, it's just a comversational english, which means only when people are talking. If you write wanna instead of want to in your english paper or essay then you are wrong.
就像廣東話一樣，我們有書面語和日用語，好像我們話：屋企 書面語就是家
EXAMPLE:
I wanna (want to) study.
I wanna (want to) go shopping.

3. first, gramme is WRONG SPELLING!! correct=grammar
"is it used commonly in the USA AND Britain."
or
"is it common in the USA and Britain."

it's ALWAYS "THE USA" not "USA"
British= 英國人 Britain=英國

oh i see = I understand / I get what you mean / I know it

wanna = want to. e.g. Do you wanna play football? ( Do you want to play football?)

The above expressions are NOT chinglish. It's very common in day-to-day English conversation.