Thanks a lot for your feedback ! :)
I uploaded a new version which should make sticking to wall less problematic: now the character stay stuck if you don't input anything, you can unstuck it either by jumping or by moving to the left or the right long enough. I hope it feels more natural this way !
As for the big jump of level 4, it is not possible to jump over it with a simple jump, but there is a way ! :D You can however try level 5 without completing level 4 by selecting it in the menu ;)