I dont want to sound offending, but.. I honestly don't understand whats so difficult on creating a simple room. I know this isn't helping but seriously... 6 months and can't even create a room out of blocks? Also, your profile says you've only been on AT for 0.1hours, so I'm not sure why you are speaking of "6 months" (maybe you've been offline in steam all the time while mapping, this would explain it).
I guess you have to describe your problem a little further or send screenshots/vmf-file so we can actualy help you.
I got 2nd Steam account, silly... one for gaming and talking to friends, one for modding and testing stuff out without people writing to me every minute. Also, first when I tried on my account, I was doing it off-line as you actually thought of, but it'd never show 6 months because ofc it's time which took me figuring stuff, mostly watching tutorials etc, the actual doing in hammer takes alot less time.
And as for my problem - mostly when I try to test it there is an error, don't remember it, I simply can't test it, and I even put survivors in it somehow, some tutorial explained how to, but even though I put survivors and made basic point A to point B cube, I couldn't test it nor save it. I tried for 6 months, from August last year till February this year, and always was same result - whatever I did, error, cant save, can't run a test on map, nothing.