update App.js

 import React from "react";
 import GlobalStyles from "../Styles/GlobalStyles";
+import Header from "./Header";
+import Image from "./Image";
+import Grid from "./Grid";
 
 export default () => {
   return (
     <>
       <GlobalStyles />
-      <div id="App"></div>
+      <Header />
+      <Image />
+      <Grid />
     </>
   );
 };