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.

  /*--------------------------
  preloader
  ---------------------------- */ 
  
  $(window).on('load',function(){
      var pre_loader = $('#preloader')
  pre_loader.fadeOut('slow',function(){$(this).remove();});
  }); 
  
  // meanmenu
  $('#mobile-menu').meanmenu({
    meanMenuContainer: '.mobile-menu',
    meanScreenWidth: "992"
  });
      

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

Thanks