There is a lot of ways how to learn Kotlin. Language reference, tutorials, video tutorials, online courses and much more. And now also Kotlin Edu.
Kotlin Educational Tools is Android Studio Plugin that helps you learn Kotlin by giving you small tasks. Read task description, write code and check. And if you cannot find the solution, you can click on Fill answer placeholders to get a right answer. Task description usually includes a link to Kotlin reference page, so you get right at the page with all you need to study to finish a task. It first looks like this.
And when done, like this.
I haven’t spent too much time playing with this yet but it looks promising. Check it out at https://www.jetbrains.com/education/kotlin-edu/.