I'm about to learn Kotlin and have few questions

My background is in JS/TS, and my goal is to build apps with Kotlin. I made a few apps with React Native years ago but ran into limitations. I’d like to switch to Kotlin, so I have a few questions:

• Is it better to learn pure Kotlin first or jump straight into Android development?
• How long does it usually take to learn the basics of Kotlin well enough to start building an app?
• Where did you learn Kotlin from scratch? Any step-by-step resources or courses you can recommend?