How to make bootstrap menu vertical when collapsed?

Question

css

Hello everyone, how to make Bootstrap menu vertical?
The menu became horizontal after I found a code on the web to make the menu centered and inserted this code.

style.css :
.navbar-nav {
float: none;
text-align: center;
}
.navbar-nav li {
float: none;
display: inline-block;
}

Now when the window is minimized, the menu instead of being under each other, has become horizontal. ( How to fix it?

Answer 1

style.css :
.navbar-nav {
float: none;
text-align: center;
}
.navbar-nav li {
float: none;
}