Hide 3-bar hamburger menu icon everywhere except phone

Is there a way to hide the 3-bar hamburger menu icon everywhere except when the layout is 600px or less?

This does the trick for 979px and above, but I don’t know how to make it work for 600px and above:

.btn-toggle-nav { display: none; }
@media (max-width: 979px){ .btn-toggle-nav{ display: block;} }

My page is https://www.ecsl-sports.eu