Will and Going to

There are two ways of writing the phrases in future:

Will:
We use will when we decide to do something at the time of speaking
It's compost by:
will+ the infinitive of the verb of the action (without to) + rest of the sentence
Ex: Did you phone Lucy?No, i'll phone her now.
With will we can form a negative and interrogative sentences:
Negative form: subject + will not(won't) + the infinitive of the verb of the action+ rest of the sentence.
Ej.: Kate will not (won't) wash the dishes tomorrow.
Interrogative form: Will+ Subject+ the infinitive of the verb of the action+ rest of the sentence.
Ej.: Will Sophie wash the car tomorrow?.

Going to:
We use going to to say something that we have already decided to do in the future.
It's compost by:
To be(present) + GOING TO + the infinitive of the verb of the action
Ex: John is going to watch a film tonight.

Also, going to have the negative an the interrogative form:
Negative form: Subject + to be + not + Going to + the infinitive of the verb of the action + rest of the sentence.
Ex: John is not(isn't) going to wach a film tonight

Interrogative form: To be + subject + Going to + the infinitive of the verb of the action + rest of the sentence
Ex: Is John going to wach a film tonight?

Credits: an exercice book and me.