I do want to preface this by saying I've seen Arrival a few times and love it- but think I've missed a few things.
I know she's seeing the future ahead (child, child dying etc) and the aliens are saying they have come to help earth as they themselves will need to be helped in 3000 years.
But what did they help earth with before they disappeared again?
And also I think their smoke signs should have been called very complicated emojis. 🤣