gonna = going to It is slang for 'going to' I'm gonna buy a new car= I'm going to buy a new car

"Gonna" is the contraction or informal form of "Going to" not "Go" For example: I am gonna(going to) do this for you but you should pay me. She will gonna(going to) pay for the damage so do not be bothered. I hope it could help you in choosing the best answer for your query. Thank you.

At first--- I'm going to describe 2 words between go & gonna : Go mean like you want to go somewhere or other places. Ex : I want to go shop ( In present tense ) Gonna mean like you act or talk about something that doesn't happen yet and probably untrue. Ex : I'm gonna play football ( In future tense ) Gonna doesn't make sense : It could be or could not. Hope you're clear between Go and Gonna.

I hope it helps!