Due to logo, the header size of ours is a little bigger than usual. You can change the value of the offset variable at line number 214 of js/main.js file and see if that helps. You should look for a line which reads like this –
preventDefault: true, easing: 'swing', speed: 700, offset: -50, exclude: ['.external a'],
and change the offset value until you find the scrolling does not lead to overlap of the contents.
You can also try changing the value of width of the logo image for the sticky menu this way through Custom CSS pasted in theme options –
#header.sticky img { width: 50%; }