"Wanna" is a slurred version of "want to" or "want a". eg. I wanna hamburger! I wanna go home! A lot of learners use it thinking it makes them sound more "natural", but unfortunately it has the opposite effect - the speaker starts making mistakes that don't happen when they use "want to", and it can even make the learner sound childish. I don't recommend using it unless you are completely confident and relaxed with standard English. Of course, you never put it in writing unless you are quoting someone.

Wanna is slang :-)

I agree that you shouldn't write these words if you want to be taken seriously, but do learn to use them in friendly conversation. It's a great indicator of fluency and natural English when you can correctly use words like 'wanna', 'gonna', and 'gotta'. I personally believe it's a big mistake to keep ESL learners away from slang and discourage them from using it in the proper places. The proper place for these words is in informal conversation, which I hope you find yourself involved in a lot.

Wanna= Want to... i want to learn English= i wanna learn English so after wanna" u have to use a verb.

I presume you are asking about these two phrases, for example: I want to go home. I wanna go home. The first is correct, normal English. The second is not. 'wanna' is not a word. It is a transcription of what you hear when somebody is speaking fast. It is NOT the same as 'can't' or 'I'm' or 'doesn't'. These are correct standard contractions - 'wanna' (and 'gotta' and 'gonna') are not. Educated native speakers never write these forms. The only places where it is (just about) ok to write 'wanna' is in song lyrics and maybe cartoon dialogue - because these are imitations of speech. But you might notice that it's not the intelligent people in cartoons who have 'wanna' coming out of their mouths in speech bubbles - it's usually spoilt and annoying children. If you write 'I wanna', it's the same as saying 'I'm lazy, uneducated and a little bit rude. My English is bad and I don't care'. I'm sure that you don't want to give that impression to people, so please don't use it. If you want people to take you seriously, you should write normal English.