Content div going over fixed navbar
In order to fix this you need the property z-index
defined by W3 that specify the level of the element. Try this:
#navbar {
background-color:#990000;
position:fixed;
z-index:1; /*Add this*/
width:100%;
height:50px;
text-align:center;
vertical-align:middle;
line-height:50px;
top:0px;
}
If you're using Bootstrap 4, the .navbar background is clear and can be covered by some elements. Setting the z-index won't work. Use a background color, e.g., .bg-white.
<nav class="navbar fixed-top navbar-expand-sm navbar-light bg-white">