Defrauded out of my Spanish property

In 2016 I was approached with a part exchange deal on my Spanish home. The buyer asked me to help him to avoid paying purchase tax by not declaring the other properties involved, only the cash element of the three way deal. He paid the cash element of the deal up front even before the other properties were completed. Then I discovered that the other properties were not legitimate & refused to to accept them. He took me to court in Spain without my knowledge & lied that he had bought my house for the value he had paid (circa 45%) & he convinced the court, who judged in his favor, so he was awarded a 400k estate for 145k. His lawyer lied in court & backed up his claim. He now owns my house. What can I do?