You can reposition the hamburger with custom CSS...
.g-offcanvas-toggle {
left: 2rem;
top: 2rem;
}
To create a custom CSS compatible with Gantry 5 please read this
http://docs.gantry.org/gantry5/tutorials/adding-a-custom-style-sheet
.
Remember to recompile CSS from base outline too.
Regards, Mark.