To improve in drawing comic books and graphic novels, start by reading a lot of them. Analyze how the stories are told, how the panels are arranged, and how the art and text work together. Experiment with different art mediums too, like digital art or traditional pen and ink. This can expand your creative options. Try to tell your own short stories through comics. It'll help you develop your storytelling skills as well as your drawing abilities.
Practice regularly. Draw different characters, poses, and scenes every day. Also, study the works of other great comic book artists. You can learn a lot from their styles and techniques.