Hajar Fahad wrote:
how to do back up when I can't open lap...
You can do it like noondaywitch says or you can do a better approach which is to install OS X on a external drive.
Your going to have to erase and rebuild your boot volume anyway.
So if you do this on a blank powered external drive first, then option key boot the computer from it, you can grab just your FILES off the internal drive which has a higher chance of success (and faster) with a problematic drive than copying the whole thing you can't use anyway and incur a higher chance of failure in Disk Utility.
If you can't transfer files normally with drag and drop methods from the external boot drive (like they disappeared from the file system) you can install Data Rescue on the external booted drive and use that to scan the internal drive for files to recover by the 1's and 0's of the files themselves on the magnetic media.
Since the external drive is bootable, you can use the computer, get online and whatever you need just like normal.
Once all your files are safe and the external drive is setup the way you want with programs, tweaks etc., then you can download Carbon Copy Cloner and clone the external drive back onto the internal one using the default settings. The cloning process does all the work.
Disconnect the external drive and reboot, set the internal drive as the Startup Disk in System Preferences.
So with this method you have a greater chance of success recovering files,
Create a data recovery/undelete external boot drive
The Disk Utility > Restore method is dangerous in the fact that you won't know what DU missed copying until you erased and installed on the original drive, unless you have another Mac laying around that you can verify the files were copied.
Once you erase the internal drive or partition, your chances of using Data Rescue to read the 1's and 0's of "lost" files is greatly diminished.
If you do have another Mac laying around, then you could use Firewire Target Disk Mode to grab files and bypass the whole external drive completely.
https://support.apple.com/kb/ht1661