Hello,

You have set margin and padding into Design section http://prntscr.com/lsysus they cannot be rewritten with CSS, you need to remove them.

You need to assign a class to the section title http://prntscr.com/lsyurz and http://prntscr.com/lsyvgx

Then create custom CSS for the desktop using this class and reset the margins and paddings for mobile.

As for the header, the row has been hidden on mobile http://prntscr.com/lsz3w6 Disable the option.

Best Regards