17 - Always Have the Rule of Thirds in mind.

14 - Because they are on the SYMBOLS sheet, once I refresh the drawing, they are automatically behind the trees (SYMBOLS TREES), in case you want the same effect behind, you will have to create a SHEET SYMBOLS hills/dune back and place it below from Symbols BACK and above Symbols trees back. That way they will also automatically go to the right place, under the trees behind.

13 - to add more colors to the drawing, select dunes and a different color, in this case I chose brown 36 (I believe), put them on the SYMBOLS sheet and choose their places quickly.

11 - Create one SHEET > SYMBOLS TREES GRASS and place it below the SHEET SYMBOLS BACK

8 - I suggest to be careful especially in the encounters of Symbols and Symbols back Sheets, Note the encounter of the Hills with the mountains are not in a perfect way. There must be attention to, using the trees, cover the imperfections.