Hi Fairuz, and congrats on getting through the 250 box challenge! I will handle your critique, and I will divide my comments in 2 sections.

Linework and confidence

Your lines look generally fairly confident, with quite little wobbling and arching when present. You seem to have achieved a good capacity for line control in your construction lines, as I don't see much overshooting in the lines that make up your box shapes. A mistake that appears more frequently in your first half of the challenge and becomes more rare in the second as you acquire confidence in the task at hand is the presence of repeated lines. Making repeated lines can become quite a gamble, as the presence of lines that do not perfectly overlap can end up undermining the solidity of you shapes. For this reason, in this course we tend to avoid repeating lines unless we have a use for them in making our shapes more believable as a 3d object, like applying line weight, which should be done only with a single overlapping line and only on the silhouette of the box. By contrast, in some boxes here like box 80, there are more than 1 repeated line that are also applied to the inner edges, likely to try and correct an unsatisfactory line. I advise you to try and avoid this attempt at corrections in the exercises of the course, as they end up often doing more harm than good, and also by not forcing yourself to correct every tiny mistake you have some opportunity to learn how to better work around errors, which can save you time and energy in the long run. Lastly, your hatching lines, while looking generally consistent and evenly spaced, suffer a bit from a lesser degree of control, as they end up quite often overshooting the bounds of the face they sit in. Hatching lines are not second class lines, and we should treat them with the same care as our construction lines.

Construction and convergence

In the first half of the challenge you seem to struggle a bit with the construction of your boxes. There are some examples of boxes with a broadly correct shape, but extension lines in the wrong direction (like boxes 15 and 26), and also boxes with actually divergent sides (as in 28, 34, 35, 36). When we are drawing a box, an object with 3 sets of parallel lines that are mutually perpendicular, the presence of a vanishing point for one of these sets means that these lines will look to the observer like they are converging away from them to a point on an infinitely distant imaginary horizon. This means that when a point of convergence ends up in front of a face of the box, we are not looking at an object with rectangular faces, but with trapezoidal faces, i.e. boxes that do actually physically converge at some point. I wanted to make this point clear as it is fundamental to correctly apply linear perspective, even if you eventually understood this on your own as it looks like. This mistake in fact disappears as you go on with the challenge. The solidity of your boxes also improves during the course of the challenge, starting off as sometimes a bit wonky in the beginning, with boxes with some stray divergent line, and ending by the end of the challenge as generally beliavable 3d shapes. The precision of your convergence could use some further improvement, but that's something that you will naturally achieve through further practice. The back corner of your boxes lines up usually less precisely than the other sides, and this is quite an easy and common mistake since the back corner is where mistakes pile up when constructing a box from the front. I will link here some advice I gave in another critique on how to try to tackle this specific aspect of a box (scroll down to the reply with an imgur link): https://drawabox.com/community/submission/87XZS5GL

Conclusion

I feel that, even with some aspects to work on a bit further, you have grasped by yourself the concepts that make the bigger picture of this challenge. As such, I think you are ready to move on to lesson 2. However, before moving on, I noticed that your boxes stop at 244. I don't know if you forgot to post your last page or forgot to do them, but before marking your lesson as complete I will ask you to post the final 6 boxes. If you didn't do them, I'd ask you to try and improve a bit the precision of your convergence through careful ghosting and, whenever possible, extend the lines all the way to the VP. If however you already did them, I will not ask you to redo the page, but simply post them.