Recreating a 30-minute game is a great start to improve your mapping, however, you have a lot of improving to do.
1. Never.. EVER use a sky for your wall textures. I heavily recommend thok barriers, they will allow you to use the sky and let the user know how far they can go.
2. The levels are very short but the themes are split into acts. This is both a problem for your map and your recreation, as beating a 3 second map is very boring, and is not how the game really works. There is only 1 large level per stage in the original, so I would make 1 large level instead of 3 tiny ones.
3. Enemy spam and object placement. This takes the icing on the cake for your issues, I do understand Kirby faces a lot of enemies at once sometimes but your enemy placement is WAY too much, this combined with the thin very liner path makes this pack a struggle for enjoyment. While this is not really too big of a deal, there should really be less trees as well; and the stages that do include ring boxes are poorly placed and are just out there, same with the lives monitors as well.
4. The brightness is very heavy, to the point where some stages are unseeable, do not use brightness like 0-150, go for something like 250, or 230, this gives you detail on the shading without going hard on it, use a number like 10 when going through something like a tunnel/cave that leads to a teleporter.
5. The most thing you should see of all is Sev's Zone Builder tutorial, and the wiki. You need to pay attention to some tips and general help he can give, and the wiki will help you with questions such as "How do I import custom music to my mod? How do I name my levels? How can I make it so it only shows my levels in a save?"
In general, you really do need more practice and help, don't worry though, once you get the hang of it you'll see how much you've improved! Please do not let this message worry your or bring you down, I only want to help you improve. But, before you do Kirby's adventure, play around and make mini maps that will help you learn how things work. If you're stuck, try the wiki like I said. Not only does it tell you what to do, but it also gives you a file that helps show you how a specific thing works. I do hope to see more from you once you do!