Thanks for your input. Will take a look at it.
You're supposed to briefly let go of the run buttons as you come to the shell.
After the thwomp you wait at the lava. A grey shell will pop up in the lava.
Alright cleared it. Honestly it's a good level, it is very fair. The on/off switch part was actually fine. It was me fucking it up by trying to go on the fire bar. Once I realized you didn't need to it was fine. Hard but not nearly as much as I was making it. The grey shell though, maybe it is just me but I think that needs an indication. I kept trying to figure out what to do and never saw it. Sometimes it didn't even spawn when I waited. That needs better sign posting imo.
After the check point is actually very reasonable. Died maybe 4 times total. Good level. In future levels just make sure its relatively obvious what the player needs to do for all challenges. It doesn't take away from the difficulty. You did that pretty well for the majority of the level.