I need help with this simple jump code for mobile

As you can see in this link, a game “line runner” simulates a simple animation.

I’ve noticed that in my game, If you hold the jump button? a little longer?? the character actually stays in the air for a little more.!
I have made my game with animation, created a moving camera and blocks.
I’m not good at coding. Could somebody provide me some examples?? or anyway someone can help me with this problem??
Thanks in advance

Don’t post duplicate topics please; it’s against the rules. Also this has nothing to do with iOS development.

–Eric