No Administrator Account and Single User Mode not Booting

Hi, got a MacBook Pro (2018, Four Thunderbolt 3 Ports) with macOS High Sierra Version 10.13.6

Not really sure what exactly happened but currently got no admin account. Tried all procedures I found online, but nothing worked for me.

Seems like only option is to use the SUM but won't boot at all. Will go straight to the User Account. Though it will show all those text that they say online but can't get to to terminal or command line. Tried to use the Cmd+R and open terminal but still no luck.

Also, it says that FileVault is turned on the disk "Macintosh HD", is this a sign that no chance of fixing this? Really need your help with this. Thank you.