These are my notes on important grammatical concepts about the Kannada language. They are mostly based @correctKannada's YouTube series. The primary audience of these notes is people who can read/write both English and Hindi, but I think even non-Hindi speakers can benefit from them.
There are two main reasons why I wrote these notes:
These notes use the Devanagari script for Hindi and the Kannada script for Kannada. Even if your main reason for learning Kannada is only to speak it, I still recommend that you learn the Kannada script. This is because many useful resources (e.g., Google translate, @correctKannada's video series, children's textbooks) use the Kannada script. Learning the script will probably take 2-4 weeks with spaced repetition), which is much less than the time it will take you to properly learn Kannada. Nevertheless, these pages use a tool called Trin to transliterate Kannada to Devanagari (look out for the ट्र icon in the notes), so you can start reading them even without first learning the Kannada script.
These notes only cover grammar. You'd need to pick up vocabulary from elsewhere, e.g., the Kannada wikibook. I recommend using a spaced-repetition app like Anki to memorize stuff.