I am going to do something = I have already decided to do it , i intend to do it

Mr Adiani : There is a film on TV tonight . Are you going to whatch it ?

Mr Joulayii : No , i am tired. I am going to have an early night .

Mr Rezvani : I hear Mr Soleimani has won some mony . What is he going to do with it ?

Mr Allahbehdashti : he is going to buy a new car .

Mr Ejtehadi : Have you made a coffee yet ?

Mr Soleimani : I am just going to make it . ( just = right at this moment )

Miss Bordbar : This food looks horrible. i am not going to eat it .

We normally use I am going ( present continuous ) when we say what we have arranged to do .

I am going to do something = i have decided to do it . ( but pehaps not arranged to do it )

MJ