To get past Activation Lock, you must enter the Apple ID used to lock the Mac, and the associated password. If you are the original purchaser of the Mac, bought it directly from Apple or an Apple Authorized Reseller, and have proof of purchase that is satisfactory to Apple (showing your name and the Mac's serial number), Apple MIGHT consider releasing the Activation Lock.
Absent convincing proof that you are the legitimate owner, they will not.
How to remove Activation Lock - Apple Support
If you cannot provide the credentials to remove the Activation Lock, and Apple declines your request to remove the Activation Lock, it would be very unethical for you to "sell this" (as you say that you would to) to someone else who does not know that the Mac is Activation-Locked. If you cannot unlock it, they certainly will not be able to do so.
P.S. - If you got this Mac second-hand, you may want to read
The All Too Common SAD Reality of Buying a Used iPad/iPhone – Apple Community
Although written about iPhones and iPads, much of it also applies to recent Macs.
