trouble to login

The issue is kind of weird/complex, and I’m just the last person of a chain of people who have touch this website.
A friend of mine (Person A) would like to remove his page http://www.copenhagengastrotours.com – make it not visible (a maintenance-page is fine), but to understand the issue, there is some background info needed.
Person A asked Person B to help him setup the site. Now Person A would like to make the page invisible, so he asked Person C to help him out. Person C found a guide online stating you could just remove your [url].com, so login at wordpress, under General in Settings, you see ‘WordPress Address URL’ and ‘Site Address URL’, from those two links, he deleted the .com, meaning now it just states copenhagengastrotours, and that’s it. Okay, but if you enter copenhagengastrotours.com, you still see an very retro/old-looking webpage (which Person B may originally have made when he was asked to setup the website, according to Person C this is not the proper layout, and while he was working on the page, it looked nothing like that).
Okay, now enter me (Person D). I would like to log in, back insert the .com at the two URLs and just install an maintenance-plugin. BUT. When I enter copenhagengastrotours.com/wp-login.php, and insert the login-information and hit ‘enter’, the page then loads to this: http://www.copenhagengastrotours./wp-login.php – a page with no server-indication, there are no .com, and my browser states it has issues loading the screen.
I know it is a long story, and maybe I only need to say, I have issues logging in, but I felt a need to set the frame – several people have worked on this page, and a fuck-up of some kind, could have happened at any point along the chain.
But the question is, how do I ‘fix it’, so I’m able to log on to the website?