GRUB problem (Inspiron 3052 + Ubuntu 14.04)

Hello.

For some unknown reason, my Inspiron 3052 failed to load Ubuntu 14.04 (may be children did something, but they keep silence). All what I see was "grub>" prompt.

I'm not guru in Linux, so scanned Internet what to do.

I've typed "ls" and found 5 partitions. I didn't know, what partition was correct, so tried them one by one and on the 3rd found some filesystem. I've typed 

set prefix=(hd0,3)/boot/grub 
set root=(hd0,3)
insmod normal
normal

After last command Ubuntu Recovery was launched, did some unknown work and reboot. So I have got "grub>" again.

After several tries, I've found, that correct partition must be 4, but probably due to previous run of Ubuntu Recovery, all users data was lost (((( , Ubuntu runs in installation mode and ask me about new username, etc...
After installation it failed to see Network (say something like "Not compatible with current version"). 
I've tried to run it in safe mode with Network support (and it see the Net !!!), update packages (they was really downloaded from Internet !!!), but after all updates, Network still unavailable in normal mode.
The only package I failed to update was "Dell xxx" (sorry, don't remember the correct name), Ubuntu says something like "Untrusted source"

So, 2 questions:
1) Am I totally lost user data by running Ubuntu Recovery, or there is a chance to restore it?
2) How to fix network error? In "Settings/Network" I see only Proxy configuration