How to create Multi-Site support from different pages of the website

My purpose is to create website URL for each user of the website for example actual website URL is https://ift.tt/2DO3u4Z but I want same page open by "www.username.com"

Few more examples are "https://ift.tt/2S2C1zF" should be open by "www.username2.com" and so on for other users

I will buy those domains

I am using Angular 6 for front end and rest APIs are in PHP