Horisontal scrol bar on centar when section is selected

I need help.
i am trying to center the horizontal scroll button to the center when it is selected. When the button leading to the section is on I want it to be in the center. Thanks a lot!
NOTICE: ITS JUST FOR MOBILE. cant see on computer view.


Here is my public share link: [LINK]1
(how to access public share link)