Hi. I’m only 18 and it’s terrifying to have spondylolisthesis. I want to know if it can be reversed through effective physical therapy? What must I do

No. spondylolisthesis is a malalignment of vertebral bodies and requires surgery to correct if producing symptoms of cord compression. While physical therapy may strengthen muscles and alleviate symptoms somewhat, it does not cure the condition. See neurologist to assess for symptoms and whether surgery is required or not.