First, you can try to draw to the end with other pencils instead of a pencil. Second, you can adjust the strength of the pen to make the whole picture different in hardness and make it look too rigid and without ups and downs. If it gets worse, sweep it lightly and sharpen the pencil in time. There must be several objects in your picture, not just one. They are totally different in texture. You can't draw the same line on it with a pencil. So the hardness of your pencil must be different. You should practice drawing straight lines as long as possible. When drawing lines on an object, the inclination of the pencil should be as slow as possible. Draw lines with a pen tip at smaller intervals. Don't hesitate to draw a line neatly. When you see the background, you should also wipe it with a paper towel. Be sure to replace the pencil with a lighter top line after wiping. This will be much better. I am an amateur and don't know much about it.