A gorgeous German fitness influencer plans to run more than 5,200 kilometres along the German border in just 140 days after being playfully challenged while drinking in a local Biergarten. Joyce Huebner, 35, poses in undated photo. She will run more than 5,200 kilometres (3,231 miles) in 140 days. (@runninggirl.joyce/CEN) Joyce Huebner, 35, says she regards her project as a motivation for couch potatoes. She starts the run in the…