How are you drawing them off plane? Well, since you’re drawing off axis, it’s pretty easy to do. Perhaps the easiest way is to draw a large rectangle above the terrain and draw the lines on it to start. You can apply a temporary transparent material to the face so you can see through it and then worrk from a top view with the camera set to Parallel Projection.
Before you do that, you should correct the reversed faces, make groups or components of your buildings and other loose geometry, and you should fix the axis orientation. You managed to ball up the axes so the solid blue runs down. It should run upward.
It should look like this: