All these phrases are very informal. "I'am gonna talk to him' is actually "I am going to talk to him" - speaking about future plans, intention to do something. "I've gota go" - "I have got to go" or "I must go". "I wanna hold your hand' means "I want to hold your hand". "Get outta here' - "get ot of here" which means, go away. "Gimme a break' - "Give me a break", don't bother me, or stop talking nonsense. "Lemme go" -"let me go" It looks like all these phrases are from a book on pronunciation because that's how people talk.