I lost all of my hardrive file, even mac os x
how to re-install mac os x lion 10.7 in my mac but i dont have its original dvd .. what to do?
Find a friend who has a Mac and you'll need a USB thumb drive (32GB or larger). Using his Mac prep the thumb drive by formatting it with GUID & Mac OS Extended (Journaled) partition. Then download from the Apple Store (if you friend doesn't already have it) the OS-X Yosemite installer (do make a backup before you use it).
Using it install OS-X onto your thumb drive. Now test it by restarting your friends Mac and holding the Option key to select the thumb drive to boot up from (don't panic it will be slow). Once it starts up copy from the Mac the OS installer onto your thumb drive. Shut down your friends Mac and take off your thumb drive.
If you want to try to recovery your drive - Boot up with your thumb drive and run Disk Utility here we only want to repair the disk and permissions see if the drive can be recovered. You may want to have your friend download this app: Data Rescue ($99 US) and install a copy on the thumb drive.
If you just want to rebuid your drive take your thumb drive and repeat the process but this time you are installing the OS onto your Mac's internal drive.
The primary goal should be to extract all data from the hard drive that has been erased/formatted / deleted (but not wiped)**. But to do that you require a booting macOS. Unfortunately, when a hard drive is formatted or deleted entirely (removing macOS itself), the Mac hardware will only become a showpiece. You cannot make it run since you lack an original DVD or a bootable USB to start the Mac. As said above, data recovery becomes a primary object before you reinstall macOS. Bootable data recovery is possible with a file recovery program that provides a bootable DMG file of macOS with the copy of the software. Once this bootable DMG is acquired and made into a booting USB drive, you can start your Mac and select the bootable drive (using Option key) to select boot disk. The data recovery through boot disk targets the Macintosh HD (which now acts a seconday drive) and perform recovery of files.
Once data is all recovered and safely exported to another media you can create another bootable macOS USB and re-install macOS on your machine. Later, reinstall all the data recovered in the bootable environment. How to create a bootable macOS Sierra USB drive.
Note** In case of a wiped hard drive, file recovery from Mac will be impossible since secure wipe bombards the hard drive sectors with 0s and 1s resulting in complete removal of the contained information. With no information present on the hard drive blocks, a data recovery software will find nothing to recover. Which is why it is best to create multiple back ups for your Mac either through Time Machine, Clone or Cloud.