How to empty Macbook13"Mid2010 (High Sierra10.13.6) my own information

Make sure you have Filevault enabled if the laptop is using a hard drive since Apple's instructions that @ku4hx linked assumes either the Mac is using an SSD or has Filevault enabled on a hard drive. Apple never considered the possibility of the Mac only using a hard drive without Filevault.

I highly recommend creating a bootable macOS 10.13 USB installer as well just in case you have issues with Internet Recovery Mode (Command + Option + R).

If the laptop is using an SSD, or if Filevault is enabled on a hard drive (and encryption process has completed), then just perform the simple erase as outlined in the Apple article @ku4hx linked.

A simple erase of a hard drive will leave data behind which only requires someone with a data recovery app the ability to recover many of the files. An SSD work differently so this is not an issue, and Filevault encrypts the data so when a simple erase is performed the Filevault decryption key is erased making it impossible to access any of the encrypted data even when using a data recovery app.

If your laptop uses a hard drive and you have already performed a clean install, then you can just enable Filevault now....wait for encryption to complete, then perform the clean install process once more. If your laptop uses an SSD, then you are already Ok.

What to do before you sell, give away, trade in, or recycle your Mac - Apple Support

seppo275 wrote:

Thanks a lot of answer. I have owned Macbook only one week and that is why I have so many difficulties.

I tried to make bootable stick but had no success.

At what stage did you have a problem? If you had a problem with the Terminal commands, then post a screenshot of the Terminal window showing the command used and the error messages. Did you try making the USB installer on this Mac or another Mac...if another Mac, then what is the exact model of that other Mac?

Also, the USB stick could be bad. Macs can be picky about the drives used for booting and unfortunately the quality of many USB sticks is extremely poor. Depending on the USB stick being used, you may need to try using another one especially a different brand.

I tried to push at the same time Command + Option + R with no action. I do hope that buttons were OK?

Correct, but the timing is also important. You need to press them within a second or so after the startup chime. Pressing them before the chime may not always allow the keys to be recognized.

It is also possible the built-in keyboard has a problem. Try using a wired external USB keyboard.

Command and option were next to space-button ?

Correct.

I think that mys Macbook uses SSD and Filevault is then not necessary ?

Filevault is not necessary for securely erasing an SSD. However, if you will be using this laptop, then Filevault helps to protect your data in the case the laptop is lost or stolen so having Filevault enabled is usually a good idea.

The bootable flash drive is to designed to get you out of the very predicament you're in right now ... its use properly reinstalls the OS.

Full disclosure to the next owner is the proper thing to do. But your asking price will need to be quite low for a non operating Mac. Basically you've created a parts source at this stage.