That was a very well done Run Knu 
I don't really see any major improvements that could be done.
The only thing I could say now is that it's not really needed to change the view so much when you're the Stone Ball in the area at 02:37
Besides that, nice Level 5 Run.
BTW, what's wrong with the sound?
EDIT:
I just checked Level 5 again and now I can really tell you about an improvement
First a little improvement.
At 00:48 you can roll over the top (Right) rail and drop on the platform which is a little faster.
Bigger improvement.
You can finish the level almost exactly the same as you did but without dying (But it's also a little more risky).
When you've transformed into the Paper Ball at 03:22, go to the platform on top just after the Wood Transformer and then drop on the pushable wood thing below and then drop next to the 2 boxes on top of each other and cornerhop
I don't really see any major improvements that could be done.
The only thing I could say now is that it's not really needed to change the view so much when you're the Stone Ball in the area at 02:37
Besides that, nice Level 5 Run.
BTW, what's wrong with the sound?
EDIT:
I just checked Level 5 again and now I can really tell you about an improvement
First a little improvement.
At 00:48 you can roll over the top (Right) rail and drop on the platform which is a little faster.
Bigger improvement.
You can finish the level almost exactly the same as you did but without dying (But it's also a little more risky).
When you've transformed into the Paper Ball at 03:22, go to the platform on top just after the Wood Transformer and then drop on the pushable wood thing below and then drop next to the 2 boxes on top of each other and cornerhop