Making my page responsive

Hello ! I just started a new project to train and get some experience, but I have a problem to make the page responsive.

I’m using React and bootstrap (Reactstrap)

The page is responsive when you resize only the width, but when you resize the height, the elements just go to the top and disappear, without the possibility of scrolling.

Here is the page :

And here is the code :

Thank you in advance !

Comments from the source:

      This HTML file is a template.
      If you open it directly in the browser, you will see an empty page.

      You can add webfonts, meta tags, or analytics to this file.
      The build step will place the bundled scripts into the <body> tag.

      To begin the development, run `npm start` or `yarn start`.
      To create a production bundle, use `npm run build` or `yarn build`.

So you need to add overflow-y:scroll; When you use someone else’s CSS its good to read it.