How do I stop my navbar from deforming when resizing browser window

Question

I have a problem with my website, I want it to stay the same width and height no matter the window size, i managed to do it with pretty much the whole body but the navbar.

My code for the resizing to stop looks like this so far:

<div style="min-width: 960px; margin: 0 auto;">

I am using bootstrap 3, classes for my navbar:

<nav  id="navbar1" class="jumbotron navbar navbar-default ">

Sorry if I am asking something obvious, but I've been learning web dev for a month or so. EDIT: my navbar code

  <nav  id="navbar1" class="jumbotron navbar navbar-default ">
  <div class="container-fluid col-lg-12 col-sm-12 boxy col-xs-12">
    <div class="navbar-header">


      <a id="znacka" class="navbar-brand" href="#"><strong> PIZZA NICK'S</strong> </a>
    </div>

    <div>
      <ul  class="nav navbar-nav">
        <li id="polozka_navbar" ><a href="#">Pizza</a></li>
        <li id="polozka_navbar"><a href="#">Cestoviny</a></li>
        <li id="polozka_navbar"><a href="#">Galéria</a></li>
      </ul>

      <form  align = 'right'>
      <button  id="facebook" class="btn btn-primary" onclick=" window.open('https://www.facebook.com/pizzanickstopolcany/','_blank')">Facebook</button>
      </form>
        <div align = 'right' id="cisla">
          <table>
            <thead>
              <p> Volajte hneď teraz! <br>0917 711 216 || 0948 218 886 </p>
            </thead>
          </table>

        </div>
 </nav>

Thank you so much.