"Stage" comes from the French "étage" (old form estage) meaning: "lantai" (sebagai lantai bangunan). So, figuratively, it means a step. And we could understand the various meanings, from this French etymology.
Stage: Arti 1. Penyanyi itu bernyanyi di atas panggung = the stage. (The "lantai" meaning is close)
Arti 2. Figuratively, when you go to a floor (first floor) to another floor (second floor), it means a progress, you pass a step. So "stage" is a step (langkah)
Figuratively, it can means tingkatan (level) or step (tahapan).
It's very used in video game. There are stages. Https://en.wikipedia.org/wiki/Level_(video_gaming)#Bonus_stage
In this Duolingo sentence, there's a high probably it's video game.
Stage=level. = tingkat
But maybe if it's some kind of other games, like a race, it could be "tahapan"?