Previous owner ID is still linked to my macbook

What you can or cannot do depends upon the age and model Mac. Unfortunately Apple does not include a place in the profiles on this forum for the age to be included and this is often essential in knowing what can be done. Macs made in the past couple of years have extra security features which mean you really have to know the log-in information for the Apple account that was set on the Mac.

Click on this link to read about 'Activation Lock for Mac' --> https://support.apple.com/HT208987

If this is an Intel model Mac you can erase the whole computer, reinstall macOS and then upgrade it:

"How to erase your Intel-based Mac" [was: "Use Disk Utility to erase (format) a hard disk, flash drive, or other storage device for Mac."]

https://support.apple.com/HT208496

I very, very, very much doubt Apple would tell you the email address of the former owner if they even know it. They don't really track ownership of hardware once it is purchased. On new hardware with activation lock capability the owner is whoever's Apple ID is set up in Find My.

This is what you should check has been done before receiving a used computer: 'What to do before selling or giving away your Mac.' --> http://support.apple.com/HT201065

That's an Intel model which luckily for you just pre-dates the models that came with the extra security of the T2 chip which would possibly absolutely require the previous owner's information (activation lock capability).

I earlier posted a method on how to erase a Mac and re-install the operating system (make sure you have a backup of your files!) This document has a more thorough set of instructions that the previous owner should have done before giving you the computer:

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

There is a small possibility the owner may have set a firmware password, in which case you're in a mess because to get it removed you would have to take the computer to Apple with proof such as the original receipt from Apple with the computer's identifier information.

Note that you have been recommended a response with standard statement about what to do about a previous owner's ID that generally applies across the board to Apple mobile devices, but not all computers. We don't have the year detail about your MacBook Air but there's a long string of older MBAs that did not come with Activation Lock capability. For those older models it is possible in many cases to reset the Mac completely and set it up for a new user. I posted about that in a not-"recommended" response which tells you a bit more about what in reality -- vs. by the book - you can do.

There is nothing you can do about it without contacting him and asking him to remove your macbook from his list of linked devices.