Add custom segment client name in WordPress URL

I have a saas application backend in CI and frontend in WordPress.In WordPress based on saas client, I will show custom contain like about us contain and other details but all clients share same WordPress site.

The complete flow:

1.From backend I create new clients and set metadata like clients about the text.

2.I retrieve the value from the URL to determine the client and show the relative text on pages.

Now I simply trying to achieve a seemingly simple permalink structure customization

mydomain.com/client1 => home url for client 1
mydomain.com/client1/aboutus => aboutus url for client 1

mydomain.com/client2 => home url for client 2
mydomain.com/client2/aboutus => aboutus url for client 2