Hi! First of all, I changed the level perspective since the previous lesson, because my Z axis was not wrong 
I had a weird issue when painting trees : they weren’t showing up. After switching back to Paint Texture, everything appeared. Maybe there is a refresh thing to consider, who knows… 
Anyway, here are two views of the sandbox level with placeholders found on the Asset Store: Mobile Tree Package | 3D Trees | Unity Asset Store
I plan to create my own assets with Blender so I just used them to complete the course.
The terrain with trees. The white GameObject is a TGV placeholder - to determine if the dimensions of the terrain are correct or not 
A quick test with future camera positioning.