I mean, depending on his hosting it’d be a bad idea to contact them and say “Yeah, my Habbo Retro is loading slow”, considering retros are illegal and most hosts don’t allow it.Are you using a VPN or Proxy Service (on your server or on your personal computer)?
Please give us the specifications of your server. Where is it located, whats the included bandwidth and traffic limit.
In doubt, contact your hosting provider. But I think the problem is on clientside.