In fact, reading theoretical books is of little help to you, and you usually have to do more.
You can copy first, copy what you like, such as your favorite comics (don't look too bad, recommend those Japanese masters), comics and so on. You don't have to start with sketching, but you should start with interest. This process is to keep your hands and eyes in line. When you draw something, you should keep relaxed and avoid rigid lines. After a long time, you will gradually understand everything. Don't pursue "painting well", but pay attention to "enough". "Good painting" is endless, and it is not easy to be "enough". Just be happy!