Hello! Let me see what we have here.

Most of your extended lines are parallel. These boxes are meant to be done in 3 perspective, so their extending lines must always converge. It is somewhat difficult without a horizon line, but you can approximate. When drawing a box, try preparing your converges as if you're doing the ghosting method.

To add more dimension to your boxes, I would suggest drawing some hatching lines on the plane that faces the viewer. Adding lineweight would also help.

A lot of your lines are repeating. I see that you do plan your lines with points, but you shouldn't worry about accuracy. You need to draw your lines with confidence. Try focusing on the end point as you draw a line.

Many of your boxes are too similar. I would suggest drawing your Ys with different line proportions as well as different angles as long as they are over 90 degrees.

I hope this advice helps!