Cannot run Gmod for the life of me

Ok, so this is starting to get me angry. I got Steam yesterday and with it I got Garry’s Mod and LFD2. I downloaded the necessary amount to play GM and I did for a while but it was the basic version because I didn’t download all of the updates. I quit and went back to steam to play LFD2. It needed about 7 hours of downloading to launch so I let it go but in the meantime, Garry’s Mod, which was at about 42%, stopped downloading. All it said for the longest time was “Download starting…” so I thought after LFD2 downloaded it would start. The next day, LFD2 is finished and GM is still starting. I tried to restart steam a bunch of times and every time it would only be trying to start. Plus it would always be validating files, 1 file, and it would usually go from 0% right to 100% upon starting steam.

So then I tried to play it despite the download error. A box saying “validating files: 0%” would return and that would stay there for about 5 seconds. Then the moment it says that the validation is at 100% and was successful, another window comes up and says that the servers are busy and to try in a few minutes.

I researched how to fix it and found that I should change the download area so I tried every single area around me and it still won’t work. I also tried messing with the firewall and whatnot. No matter what I do I can’t fix it and its getting on my nerves. Can anyone help? Please?

I should add that this is on a brand new iMac with the second best processor ( I forget). The computer itself shouldn’t be the problem.

core i5?

Maybe thats the Problem.

Or the steam Servers are just overloaded.