I keep making wrong assumptions about what they are trying to say. How would one say, "Let's come back some day"?
I learned "vamos a la playa" means let's go to the beach. So I thought let's go return some day.
Remember, "ir a" + infinitive is the marker for a future event, equivalent to "going to do a thing" not going to a place.
Voy a comer (I'm going to eat)
Vamos a volver (We're going to return / come back)
Vamos a la playa (let's go to the beach)
Vamos a ir a la playa (we are going to go to the beach)
I'll see you someday (indefinite).
I'll see you some day next week (choice within a definite time).
Why is "We are going to return another day" not correct? It's common English, and seems to be a more direct translation.
There is no such word as "someday"! It's two separate words just like in Spanish --- some day! (And then they tell me I have an extra space in "some day")
I thought that my, "We go to return another day" was rather poetic. I can hear the line being spoken in a play - followed by the swish of a cape. I'm not troubled by Duolingo's grading anymore... you lose a point here and there. It's discovering surprises in meaning that keeps the Owl fun.