They are not the same. The correct form would be: - He knows his girl's gonna talk about it all day. - He knows his girl is gonna talk about it all day. When there is evidence that something is likely to happen (in the future), you might want to use this form: to be + going to = to be + gonna "Gonna" always has to be followed by an infinitive. It can only be used in spoken form, both formal and informal. In written form (also in spoken language) it will be: - He knows his girl is going to talk about it all day. In you last sentence you've used the word "gone", perhaps accidentally, because that means "no longer present". So it can't be used in this sentence. I hoped this helps.

"He knows his girl gonna talk about it all day." isn't grammatically correct. "Gonna" should be replaced with "going to" so it becomes "He knows his girl is going to talk about it all day.". "He knows his girl gone talk about it all day." doesn't make sense cause "gone" is the verb "to go" in a form that is used for the past actions. I hope it helps!

thank u Chris and Tim 🌹

This is non-standard speech. In very old movies, the scriptwriters use this type of speech for illiterate characters who have never attended school. In modern times, rap and hip-hop music glorify this non-standard speech as part of black cultural identity. Here is more information about Black English (Afro-American Vernacular English). https://en.wikipedia.org/wiki/African-American_Vernacular_English

Your first sentence is a slang way of saying things in “improper” vernacular. It is very informal but I’ve heard things like that said in vernacular that way with the “is” dropped. The second one doesn’t work. Gone isn’t used for going to in any vernacular I’m aware of.