Future forms. Formas futuras.
Be going to + infinitive. We use going to when we have already decided to do something. We also use going to to make a prediction about the future, especially when you can see or have some evidence.
Present continuous: be + verb + -ing. We often use the present continuous for future arrangements. Will / shall + infinitive. We use wil / won't for instant decisions, promises, offers, suggestions and predictions. For example: I think Chelsea will win. We use shall with I and we for offers and suggestions when they are questions.