If you want to remove the preloader animation completely from the theme, follow the steps bellow :
1) Open _layouts/default.html file and then find the code and remove that from there. <div id="preloader"></div>

02) Now open assets/js/app.js file and remove the following code from there to delete the preloader functionality from js.

  ---------------------------- */ 
      var pre_loader = $('#preloader')
  // meanmenu
    meanMenuContainer: '.mobile-menu',
    meanScreenWidth: "992"

Still if you need any help to remove or change preloader feel free to contact us.