Hey there, great work so far!

It seems that a lot of your box corners have lines that overshoot each other - particularly in the organic perspective exercise. Would be beneficial to practise ending your lines accurately at a point. It will help your boxes look tighter and cleaner.

Pay attention to perspective when drawing boxes too. In the plotted points exercise, you'll see that the end of the box that fades out to the horizon will be smaller than the end that is facing you. You need to remember this when doing exercises like the organic perspectives exercise - many of the boxes there have their perspective flipped the wrong way. Always remember to stop and think ebfore you draw a box - which end is fading out to the horizon and thus needs to 'shrink'?

Apart from that, good work! All the best!