Hi. Welcome to the forum. The post here explains the problem
You should always make regular backups of your site as described in this FAQ
Your domain should not be effected if you purchased your own domain. All of those settings are stored on the server of the company you purchased the domain from… not on InfinityFree servers.
As far as restoring your files, the admin or someone from InfinityFree will have to take a look at your site on the server.