Collapse Nav Bar on single page on mobile & scroll

Issue I am having is on a single page site, the navbar on the mobile does not collapse with the #link any ideas on the best way to do this.

Additionally on the mobile it over scrolls on the link.

here is the site https://diversemechanical.com.au/new-index.html

If you click any of the links you will see what I mean.
Thanks in advance