Home Link?

Hi, newbie here, can anyone help me on the Main Navigation Menu,

i have Home, About, and Contact Us.

but it seems, when i click About, then want to back to Home, i get this 404 error page. and if i click the Home again, then it goes to the frontpage.

Why is that? and how do i fix it? Thank you

my web is https://www.hkplawfirm.com