Described above.
Check firewall settings
I know nothing about it… I don't know what you mean, I just can do almost nothing and get stuck.
Make system restore
Did one, still nothing works.
I know how to open firewall settings, but I don't know what to do. What should I set so that EVERYTHING works as before?
Reboot is good for people with this "fast boot" feature, so press the shift key when restarting…