It’s a mixed bag. Most often the top most shown word is the one to use and the others are used in alternative contexts. But sometimes any of the shown words are usable, then one has a choice. But with new words which are orange color then upper most word is the one to use. When you see new words always look at the pull down list and use that top word.
ddb-'Ir a + infinitive is very common in Spanish. And easy, because the only verb you have to know how to conjugate is 'ir'. So if you know the infinitive of the verb, you can build the expression with little trouble. Such as: 'Are you going to bed, to eat, to swim, to read, etc.
So, using "ir + a + infinitive" we have future time sentence without reference word like 'manana', but it will be appropriate to use future verb form if the sentence contains the reference. Thank you for explanation. Why Doulingo do not teach us to use them? It was only a few sentences with future forms of verbs /or it is archaism which is not used a lot?
It depends on the sense of the sentece. If you are talking about a sum in maths, you can say: "Que vas a sumar?" but for example, if you are going to add a sentence or anything else, you have to say:"Que vas a añadir?". The difference between sumar and añadir is that sumar= sum añadir= add
In this context, añadir would only mean "write" in the sense of adding a comment or notation. And even then, anotar would be a better choice.
Don't let yourself be fooled by the dropdown menu. It lists several possible meanings, which may or may not apply to the sentence at hand.