Here is a picture showing your tank comparing to other tanks drawn by diffrent members of this forum.
The best advice i can give you is just see how others did it.
Look how tracks should look, look where should be a black line and where shouldn't.
Look where shade should be applied, look at the colors used.
And the first rule of any drawing here - FD or SB, try to avoid double black lines.
If you still have trouble doing it yourself, PM me and I will help you personally.