I know, I do use gonstruct myself I like it more then the official editor.
But it works for me. Maybe I can help.
The second building doesn't look correct. Try and add borders on the wall to distinguish difference in depth. It looks like one huge wall with grass/bushes holding the sides up.
League Of Legends PlayerServer: Eu WestName: SlapjackQ8Add me, everyone is welcome
The second building is illogical
If you look at it closely
Its completely flat but its also 3-D
Take a walk around era and see how there levels are. Then try and fix up your level.