Restore deleted AD Account locally

Hey Guys

I’m kind of in a bad spot. When I started with my first server running WS2012 R2, for some reason i activated Active Directory and promoted the server to a Domain, even doe everything if regulated by my PFSense.

So anyway, since I got a 2nd Server and chose Veeam as backup solution cross off site network for everything (sidenote: Tom’s side 2 side VPN video came in really handy, thanks for that!), I need to create a local user Account for veeam, else it won’t connect to the HyperV running on it. (At least, that’s what I think is the problem from online research)

So I demoted my Server and deleted the AD and AD Certificate Server and so on.

What happened now, is that my Admin Account I was using is not available anymore and I have to use the standard Administrator Account. However I can still see the Userfolder in C:/Users/.

My question now is, how can I restore that account without loosing any data?
There are few services running when I log in and made a lot of configurations, why I wouldn’t want to loose that.

Any help would be appreciated.

Greetings