Ok so i just updated steam and restarted it like it told me too. Now the problem is that when i am trying to start a game, any game, it tells me that it is “scanning for steam games updates” and it just says that without end, the game does not launch. Also when i try to click some were else it makes a noise that reminds me of the Wii console and doesnt let me do anything unless cancel the scan. WTF is going on i wanna play through Dangerous World mod again and this shit happens. :’(
If you start in offline mode it should let you play. At least until someone comes up with a proper solution 
the only trick I know is to delete the blob files.
Yeah it happens a lot to me to, usually when I reinstall steam. Try restarting steam, usually it resumes updating. Don’t know if it works but it solves my problems.