Perhaps you might want to consider scaling down the size of your logo to make your fixed header smaller in height, which would reduce the necessary amount of padding between the paragraphs and headers to ensure that your content would not be covered when you click on the anchor links.
Over all of the content that is below your navbar put padding-top equal to height of the navbar. That will clear your nav
For each one of your sections that is a target of your internal nav links put a padding-top the height of your navbar then put a negative margin-top same distance. That will clear your nav when you click on one of the internal links