Future

Basic rules

You use will-future when something most likely happen.
You use going to future when you made a decision to do this(it´s very probably) 
You use present progressive mostly for appointments/Dates.

Deeper explanation

How to form will-future?

The will-future is formed from the auxiliary-verb and the infinitive of the verb.

It is used in all forms will + infinitive also with he, she or it.[1]

For example:

positive:
I will go to toilet.
He/She/It will bake a cake. 

negative:
I won´t go to toilet.
He/She/It won´t bake a cake.

Questions:
Will you go to toilet?
Will he/she/it bake a cake?
     

How to form going-to future?

Going to-future will be from a form of (is, are, or is), going to and the infinitive of the verb.

To be (is, are, is) + going to + Infinitive. [2]

For example:

positive:

i´m going to use the restroom