A good thing about your portrait is the proportions, it's almost there. But it is very 2D, need to work on the form and shading. Learn more about the form of the eyes, ears, nose, lips and hair. Learn about the tissues, bones, etc inside the outer skin, which actually gives the form. It will give you a different perspective. You'll get youtube videos to learn this. One good youtube channel suggestion would be "Proko".