Apparently the early KIA Picanto models are known for having an bad roof lining which tends to loosen over the years. This was also the case with my Picanto from 2005. First I considered to fix the lining by just making a clean cut in the middle adding some new glue and press it all up again. But sins the fabric has shrunken over the years it would be impossible to get a outcome that looked good. So after some searching online I found blog-post in german with detailed description.