AL-train.jpg
Good start and a good eye for detail. Don't rush anything, just draw. But, when you feel the time is right, ease yourself into the next step. And that is...
Begin to remove outline. At present, you're relying on outline to define all the edges - stones, grassy banks, engine, etc.
Outline is entirely unnatural. Nothing in life has a line around it. Did you have a reference for this? If you did, take another look and ask yourself why you can see the edges of the stones in the tunnel's face. I'm guessing it's either because the stones are darker than the mortar, or the reverse. And if the stones are dressed and standing proud of the mortar, they probably have a shadow cast underneath them.
In the meantime, carry on with what you're doing, because that's teaching you hand/eye coordination - and that has to be first step.
Along the way as you draw, you'll find something very useful occurring. You'll begin to look at the world around you differently. I'll resort to my usual example
...You have an in-built recognition system that sees a tree as a round mass on a stick. It's very efficient. You see a tree, you recognise it as being a tree, and you move on. When you begin to draw you'll start to notice more. You'll see that a tree has holes through it that expose internal boughs as silhouettes against the sky. That the foliage consists of rounded masses; each having the highlights and shadows associated with round objects. That the silhouetted foliage around the edge of the tree usually gives a strong clue to its species. And a host of other details will gradually be noticed too.
All those details will be stored in your memory. So, the next time you draw a tree it will look more realistic than the time before - because you have more information to recall.
So, just draw and let it all happen.
I'll discus the lily later when I have more time.