Responsive website header?

Question

HTML

There is a header of the site Header and there are 4 links in it.
So I want to make it so that if the permissions are less than -520px there is such a button (Fig. 1)
that when clicked, the menu opens,
I saw this in Bootstrap, but I'm on my site I don't use Bootstrap

Answer 1

I found the answer
myself jsbin.com/fayuhoxoda/edit?html ,output

Answer 2

https://jsfiddle.net/webirus/aesfhL47/