update

app/assets/javascripts/application.js

 //= require jquery
-//= require bootstrap
+//= require bootstrap.min
 //= require rails-ujs
 //= require turbolinks
 //= require_tree .

app/assets/stylesheets/application.css

@@ -12,5 +12,5 @@
  *
  *= require_tree .
  *= require_self
- *= require bootstrap
+ *= require bootstrap.min
  */

app/assets/stylesheets/custom.scss

-@import "bootstrap";
+@import "bootstrap.min";
 
 /* mixin, variables, etc. */
 

app/controllers/static_pages_controller.rb

 class StaticPagesController < ApplicationController
-  def top_page
-  end
-
-  def favorite
-  end
-
-  def history
+  def home
   end
 end

app/views/layouts/_header.html.erb

@@ -13,10 +13,6 @@
             <li class="list-inline-item"><%= link_to "History", history_path %></li>
           </li>
         </ul>
-        <!-- <li><%= link_to "Login", "#" %></li>
-        <li><%= link_to "Register", "#" %></li>
-        <li><%= link_to "Favorite", favorite_path %></li>
-        <li><%= link_to "History", history_path %></li> -->
       </ul>
     </nav>
   </div>

config/routes.rb

 Rails.application.routes.draw do
   devise_for :users
   # For details on the DSL available within this file, see https://guides.rubyonrails.org/routing.html
-  root "static_pages#top_page"
-  get "static_pages/top_page"
+  root "static_pages#home"
+  get "static_pages/home"
   get "/favorite", to: "static_pages#favorite"
   get "/history",to: "static_pages#history"
 end