Decicions made a the moment, promises, offers, predictions,threat
1.
I will help you
2.
I bleive they will win this match
3.
Next time I will study more
4.
I will carry you back
Subj+WILL+verb inf.+complement
Intentions,predictions with evidence
1.
I'm going to visit my aunt next friday
2. Look at that cloud, It's going to rain
Subj.+to be+actually verb+principal verb+complement
Arrangements
examples
She is starting dancing classes tomorrow
In 30th of June, Joseph is fliying to London
Subj.+to be+verb-ING
Timetable, scheduled events
examples
My flight to Paris leaves at 8:00 tomorrow
Subj.+to be+verb+complement