Well, him (@ranartblog) is me :o)
You have done great. This is a complex shape.

I think the next step is to try and draw with no lines.
You can use the lines very gently, just for the structure.

Then, look for the brightness values.
Meaning, try to see how dark or light each area is, and draw smoothly with the pencil that same dark or light value.
If you press lightly with the pencil, it will be light, press harder and it will be darker.

Example:
First the structure.

Then, brightness values (no lines).