Hi USB, "We can say I'm gonna to see him tomorrow"... uh, no. No you can't. This makes no sense, even as slang English. As themax explained pretty well, "gonna" is a contraction. So you still have to treat it as "going to". Knowing about "gonna" doesn't mean you have to use it. ;) You'll find most good English speakers don't bother using this form.

It's best just to avoid using "gonna" unless you have a really good handle on the language and know the appropriate situations in which to use it. As you don't, I would suggest not using these kind of constructions.

"gonna" is not a standard English; "gonna" , "wanna" , "yeh" , ... are expressions used in TOEFL (Test Of English as a Foreign Language).

Firstly, if "gonna" = "going to" then why add additional "to"? "I'm gonna see him tomorrow". Secondly, "gonna" is a contraction of "to be going to". Like I have plans to go somewhere. Not of the verb "go" in continuous tense, which would be "going to" either.

You're from the UK. So why do you ask?