how to create multiple pages in a single repository in github? Now for a single page, I am writing code in index.html but how to create and share multiple pages links from the same repository is there any way like creating new directories or something?
Yes just create files and directories
Check the doc at https://docs.github.com/en/pages/getting-started-with-github-pages/creating-a-github-pages-site#next-steps
You can add more pages to your site by creating more new files. Each file will be available on your site in the same directory structure as your publishing source. For example, if the publishing source for your project site is the gh-pages branch, and you create a new file called /about/contact-us.md on the gh-pages branch, the file will be available at https://.github.io//about/contact-us.html.