Apple 15" MacBook Pro (2017, i7, 512GB)

The short story: I am now the completely unproud owner of a computer-shaped hunk of stuff that the seller will not take responsibility for. Bonus: I am now the also completely unproud owner of a broken charger. Details: It has taken me awhile to write this because it makes me so upset. I bought this laptop listed as in "Excellent condition". After I set it up, I checked the audio and noticed that it wasn't working well and decided to return it. I also noticed that it took a very long time to charge; I charged it for 12 hours, unplugged it and it ran out of power in 4 hours. Another issue appears to be overheating/fan--four minutes after I turned it off, the fan went on for over 3 hours. Some of the keys were sticky and the end of the charger got stuck in the laptop, then broke when I pulled it out. The REAL PROBLEM is that it locked me out after I tried to restore it to factory settings. After I tried to reboot into recovery mode, the computer asked for the firmware password. This is not the Apple ID password. It is not the login password. I had never even heard of this type of password and I certainly didn't set one or even know how. After researching online, I contacted the seller and he said that I would have had to set the password myself. I asked him to give me info on how to request the password that I supposedly set and he gave me a link to a useless Apple article. I tried entering any password I might somehow have accidentally set three hours before, previous to my period of amnesia, and looked through all of my notes on which I write clues to new passwords before I enter them into LastPass, and got nowhere. I spent hours online chatting with Apple, talking to Apple on the phone, going to the Apple store and researching. They told me they need the original invoice or password from whoever first purchased the computer. I asked the seller who said they didn't have the invoice. I found out from Apple the name of the original seller (a company those contact info is easily found online) and asked them to reach out for the original invoice or password. He didn't even respond that time. This was after the tech at the Apple store confirmed the password could have been set by the original owner. I think the most useful info Max, the seller, gave me was, "we will not be able to accept a return the a firmware lock on it." Yeah, well I would not purchase "the a firmware lock on it." After spending hours of time and energy, I didn't see any other choice except for me to eat it. And buy a laptop 2 years newer and well-functioning for $40 less.