How to remove the header overlap on all my pages?

Site URL: https://rhino-cat-dfeb.squarespace.com/faq

site password: demo

My header overlaps all my pages both on mobile and full screen view. 

When I use jump links using code the codes goes behind the header so the title of the content isn't shown when the we click the hyperlinks.  I used spacer as a band-aid solution for this but won't work on mobile. 

Also, is there a way to fix the navigation? when the screen is smaller the 'contact' goes under the other ones. 

Hope you can help.