Jumping too slow/awkward

I’m making a Sonic Side Scroller as an example for my students. I have two issues. The first is the jumping as is makes the game too difficult.

Link to the project or level: Game Lab - Code.org
What I expect to happen: Sonic will jump quickly, double jump maybe, but I need him to go up long enough for him to miss the enemies but jump smoothly enough to look like a video game.
What actually happens: Right now, Sonic jumps slowly and will only go up once when you press the up button. It’s hard to avoid the enemies.
What I’ve tried: I’ve tried changing the velocity, but then it doesn’t look right, or it becomes more difficult to avoid the enemies. I’ve also tried removing the if (sonicRun.y>299) in line 470. I’ve also tried using keyWentDown instead of keyDown.

Have you figured that out? It seems to play ok when I try it.

Mike