So if  so many div is used in navbar child, we need to use some
  JavaScript to make it sticky , 
document.addEventListener("DOMContentLoaded", function(){
    window.addEventListener('scroll', function() {
        if (window.scrollY > 50) {
  
           
    document.getElementById('navbar_Id').classList.add('fixed-top');
  
  
            // add padding top to show content behind navbar
  
  
            navbar_height =
    document.querySelector('.navbar').offsetHeight;
  
  
            document.body.style.paddingTop = navbar_height +
    'px';
  
        } else {
  
           
    document.getElementById('navbar_top').classList.remove('fixed-top');
  
           // remove padding top from body
          document.body.style.paddingTop = '0';
        } 
    });
  }); 
Need to change :
change the code navbar_id with your own navbar 
subject to change :
Understanding of code :
- Now check if window scrolled window.addEventListener('scroll', function() { ... }
 - Check if scrolled more than x amount of px if (window.scrollY > 50) { ... }
 - Select navbar element and add function classList.add('fixed-top'); to fix on top
 - Remove class fixed-top when page scrolled back to top