I agree. I tried Kotlin when I was working on an Android app and it was a pleasant experience. Somehow, everything easily makes sense and the Android Studio support for Kotlin is excellent. I followed two Udacity courses before starting on the app. If it helps anyone, these are the courses:

Kotlin Bootcamp for Programmers[0]

Developing Android Apps with Kotlin[1]

There's also an advanced android development course which is a follow up which I am going through now.

[0] https://www.udacity.com/course/developing-android-apps-with-...

[1] https://www.udacity.com/course/developing-android-apps-with-...