personal-website/themes/custom/assets/css/custom.css

 /**************** BODY ********************/
body {
  font-size:1.1em;
}

/**************** NAV ********************/

.navbar-nav .nav-link {
  font-size: 1.2em;
}

.navbar-brand  {
  font-size: 1.7em;
}

.dropdown-item {
  font-size: 1.2em;
}

/* --------------------RESPONSIVE DISPLAY HEADINGS--------------------------*/
@media (max-width: 575.98px) {
  .display-1 {
  font-size: 3rem;
  font-weight: 300;
  line-height: 1.0;
  }
  .display-2 {
    font-size: 2.75rem;
    font-weight: 300;
    line-height: 1.0;
  }
  .display-3 {
    font-size: 2.25rem;
    font-weight: 300;
    line-height: 1.0;
  }
  .display-4 {
    font-size: 1.75rem;
    font-weight: 300;
    line-height: 1.0;
  }
}