My commentary is the same as the guy below me. I found out that you're supposed to get a key to deal with the blue box, but if you've jumped down there, you can't go back up and to the right to get the key
The next level is some type of monster shooting fireballs, but the red wall that blocks you from the elver doesn't seem to disappear, even after you've dodged the fire. Jumping over it doesn't work, either