Yes, the site is offline. The Twitter account
https://twitter.com/TillKoeln has not been active since Oct 6, 2022, while domain registration is valid for another year, and expires 4th July 2024. Now there is definitely no doubt that they are actually victims of hackers and that they will never refund users.
Whois Record for Unnamed.exchange
Registrar Status clientTransferProhibited
Dates 1,461 days old
Created on 2019-07-04
Expires on 2024-07-04
Updated on 2020-02-19
It doesn't take much social engineering on Google to find that tillkoeln is the pseudonym of Till Schmitz from Köln/koeln (Cologne), Germany. He supposedly studies on Tilburg University. If it's him, he's the dumbest scammer I ever seen to expose too much about himself before scamming people lol.
Everything points to the fact that the owner is from Germany, considering that there is a legal state there, I encourage the victims of this scammer to report him to the competent authorities and if they can't get their money back, at least send him to prison.