Thank you~ hmmm tips. In general, I'd say approach studying with the mindset of trying to focus on one particular area of improvement at at time, or a direction you want to go towards. So most the time its just grinding the fundamentals right, but as you gain more control, you might want to push yourself towards a certain style or approach.
So these environment studies were specifically on how to interpret something as organic and complicated as a natural landscape into a basic outline drawing, trying to memorize the kind of patterns and shapes I would use (like oh this is the silhouette of a pine tree, etc). The reason is so i can use this information for drawing comics, which requires that kind of lineart style since in a comic it would be colored, like so:
The speed just comes with practice, and doing other studies for draftsmanship and fundamentals so that most things are just automatic. So if its too challenging or feels like you're trying to process too much information at one, just keep breaking it up into more efficient studies. Like you can practice outline drawing with human poses and perspective with environment sketches, and then try to combine them later. Example (in total these took less than 10 minutes):
Anyways haha, but of a lengthy response, but I figured telling you how I think through it, rather than just giving an answer like "step 1 do this, step 2 do that" would be more helpful. Sometimes you see the kind of stuff other artists do and it looks like magic and you think "whooahh there's no way i'll ever be able to do this, i don't have that kind of talent," but I think rather than talent, we just get overwhelmed or discouraged too easily because its so intimidating. But if you just keep breaking it up into easily digestible parts, and stay consistent, you'll eventually get it.