But I would +1 again to using the Compose Dev Challenges for learning - we specifically designed them so that one should be able to finish each from start to finish in roughly 3-5 hours, which ended up panning out in reality when we ran the challenges. If you need a challenge, I'd try to implement all three as they are different designs and have unique aspects to each. And we include all the design assets/specs:
https://github.com/android/android-dev-challenge-compose