Prevent Button from Moving

Site URL: https://porpoise-poodle-8hg6.squarespace.com/

Hello, when the window shrinks, my "Book Now" button moves and looks funny. I was wondering how it could stay in a fixed position when my screen shrinks?

I attached two screenshots. One shows how it should appear when the window shrinks and the other shows the error which is what it currently looks like when the window shrinks.

Password to enter the site = hello

Thanks!