Error for G-mod

[Travpoul]

I'm sick of this... when I open G-mod (Garry's Mod) It opens to the loading screen, then it shuts down and has this message pops up, Engine Error
Steam Error: No SteamUser.
- Make sure that steam is up to date.
- Try restarting your PC.
- Try Garry's Mod -> Delete Local Content
Please let me know if you fix this bug!

I did update steam, i restarted my computer, but, what the hell, does Try Garry's Mod -> Delete Local Content mean? Great, I have two problems, I have no clue what Try Garry's Mod -> Delete Local Content means, and I can't play Garry's Mod! If this is not fixed, I want my $10 back. Also, help me, I really want to play Garry's mod again! This has been going on for about 2 weeks now, I've gotten no help... not even a clue how to solve this. I looked on Steam but, no help. Look on the internet, no help. This is the last place I can say, help me.

[JasonMan]

How exactly do you open garry's mod?

[bitches]

Open your Steam library, right click Garry's Mod, and select Delete Local Content. This is how you uninstall games on Steam. You can reinstall it at any time, such as right after uninstallation. It may not solve your problem.