How to remove responsive for tablet?

The Oxygen Theme is really cool.
Now We are creating a website for introducing Japanese festival.
http://japan-festival.net/?lang=en
There are two responsive page, 300px and 768px.
We made a 300px one already but It’s little bit difficult to make 768px one,so would like to remove 768px.
We put comment out from
@media only screen and (min-width:768px)
to
@media only screen and (max-width:767px){.menu-toggle{display:none}}

But doesn’t work.
Please help us for this.

Thank you very much for your helping.
Yohey.