I was able to learn basic Kotlin grammar neatly.

thugwoo

This course is a course to learn the Kotlin language for Android development. 
You can learn the basic grammar and various concepts of the Kotlin language.

softcampus

Yoon Jae-seong's Google's official language, Kotlin, for getting started with programming

입문

초급

중급이상

안드로이드

Android

코틀린

Kotlin

Kotlin Overview and Basic Grammar

Kotlin control statements

Kotlin Object Oriented Programming

Various classes in Kotlin

Functional Programming in Kotlin

Kotlin Collections

Exception handling in Kotlin