It's generally a good start.

The backside of your rotated boxes is not consistent. If you look at the example, you can see that the line bends slightly and consistently every time at different rates. Just look closely at the example and move on.

The ellipses that are inside the grid are not consistent as well: there are spaces in between them, some of the ellipses are tilted in different directions.

The lines in the Rough Perspective exercise look a bit wobbly. Make dots you connect with the ghosting method.