'wanna' is a slang term used mainly in speech. It's a lazy way of saying 'want to'. It's quite common in conversation (in some dialects). I wouldn't use it in writing (unless I was quoting somebody talking, e.g. a character in a novel might speak like this).

Wanna is lazy English, and should never be used in formal situations, either spoken or written. Do not use it in exams! It can mean WANT TO or WANT A Examples: I wanna go out. (want to) I wanna pizza. (want a) Most of us use these forms when we are speaking quickly, and informally, to friends. But most of us do NOT use these forms in formal situations!

No Wanna = want to

"Wanna" is an attempt to write down the sound native English speakers make, then they say phrase "want to" quickly or casually in informal speech. In writing, it only belongs within quoted dialog, and only when the writer is deliberately misspelling words in order to convey the sound of nonstandard English--or in the titles and lyrics of popular songs. Non-native speakers should not try to say this when they are speaking, unless they have a truly excellent ear and are so advanced that they speak English without any trace of a foreign accent. If you have a good ear and listen very carefully, you will see that when native English speakers say it, they are NOT really saying either "wanna" OR "want to," they are saying something in between. There is the ghost of a dead "T" in there, and if it isn't there, the word sounds weird and may even be difficult to understand.