How do we fight this False Lien?

A mechanics lien was filed on our for sale property a person who wanted to buy the property. He has talked for a year about buying the property but when we let him know we had a cash offer from another buyer he got mad. We offered to sell him the property for $1500 less than the cash offer but he only came back with an offer $5000 less. He had been telling us for the year that he would clean up the backyard while he was getting the deal around. That did happen though he brought in someone with power equipment to do the work. He is claiming $11,000 for research on what need to be done to the property and $890 for the clean up. Or at least we think that is what the charges are for. He did not provide us a copy of the lien except grainy photos. He has not provided any invoices, bills or accounting to explain the amounts claimed. He is not a contractor. We never hired him or ask him to do any work on the property. He did in text messages threaten he was coming for his money. He called our cash buyer yelled and swore at them, Threaten to "call the prosecutor and accuse him of fraud for buy a property he has a lien on." We had to take the grainy photo in the text message to the Reg of Deeds to was able to pull the document number. Our name is spelled wrong on the lien. He is holding our property hostage until we give in to his price. What do we do? Who do we call? Can we request a judge review the lien? How do we do that? Jenny H