Connection to Steam lost Exiting -HELP-

[HomerMix]

I have the same problem and went through the whole troubleshooting with steam Tech support without any results.
They finally told me that they can't do anything and that I have to ask the 1C tech support for help.

steam tech support roughly told me this:
Do a selective startup
Disable firewall
Disable AV
Uninstall AV
Reset Steam to Default settings by clearing it.

None of these was a solution.