@kurumkan - That’s correct. The Bootstrap library is dependent upon the jQuery library so jQuery has to be loaded first. Scrollspy is part of the bootstrap library so that one is also required to get the it to work.
You have a few options to make the navbar taller (or thicker). Note that since you have a fixed navbar, you’ll have to adjust the padding for the body tag in your CSS file to prevent the navbar from hiding the top part of your page.
// This will work with your current code
You could also do what @kurumkan said above and use a custom class like navbar-custom. I try to shy away from using IDs for my elements and using !important is typically a sign of bad design and can cause unexpected results. That option would look something like this:
HTML (adds the “navbar-custom” class to the element):