The boxes and fundamental drawings look extremely lovely and those will definitely boost your skills up tremendously.
You said in your last post that you do not know where to go next. Honestly, once you told yourself that you are going to practice your fundamentals everyday, there is going to become a time when you need to ask yourself "what the hell do I even like to draw." I am pretty sure you didn't become an artist just to do straight lines and boxes all day long. I understand that in the Draw A Box curriculum, the creator kind of diverged into different things at once like humans, bugs and vehicles all of a sudden after the fundamental lessons. But that is only because once you take your foot off of the "Fundamental Zone" (you are forever always going to be in it), you can choose your own path from there.
So this is a level select stage from Shadow the Hedgehog, right? That one lonely stage over at the far left of the image is the stage you will ALWAYS start on no matter how many playthroughs of the game you play. If you want the multitude of endings in this game, you will be forced to start with this stage. This is the "Fundamental Zone" in your case cause you always have to start here when you want to be in the art industry.
After that stage, you will move up, stay straight or down depending on what alignment you chose yourself to be in (good, neutral, or bad). In the case of art, you will automatically push yourself whatever profession that YOU want to go. This is when you choose where you want to take your fundamentals and put them to good use. Let's pretend those final stages at the far right are the options you have for art professions. 1 = Character Designer, 2 = Environment and Landscapes, and 3 = Animal and Creature Artist. You can go up, down, left, right, squiggly line in the game's grid but you always end up in one of those final stages that will ultimately determine what you would like to become in the future.
All I am trying to say here is that you need to experiment A LOT in this shit in order to get the best ending for you. Do animals and machinery interest you? Start there, do animal drawings then machinery sketches. Do you see something that made you go "Oh fuckles, I have to learn how to draw that"? Like, you saw someone do an extremely good botanical illustration and now you want to study up on plants? Anyways, pick what you would like to study up on, and stick with it until you are satisfied with the final result (and keep up with your fundamental training as well).
Art is never a one way lane. (I apologize if this was too much, I had to get it out)
I hope you get your door in the industry bro!!