Just like what
kaho17 said, you need to work on proportions. You can practice by using references. Learn by imitating styles until you develop your own style. Don't just get used with tracing and/or copying, you won't learn that way, just get some ideas from other pics and you'll learn the basics. Aside from getting references, you can also use the mirror, check your own body for measurements like facial expressions, arms, hands and the like. Last thing would be practice, just practice drawing, draw use 3-5 sheets a day, draw different subjects per piece.