Jquery click function after change class not working

I think my question is really simple but I don't know why my jquery is not working. By pressing the button navIcon my navigation is animated 70px from top. Also the second classname of the button navIcon (navIconInactive) is changed to navIconactive. That works fine. But now I want to undo it as you can see in my code. I have no idea what is wrong with my code.

Thanks for your help!

Here is my code at jsfiddle: