The rare manual Heckflosse sunroof is work of art....... have you probed beyond cloth cover to see if sunroof itself has headliner intact? Maybe you can get lucky and carefully cut open the bogus cloth repair job - leaving enough material to tuck, glue and crimp along edges of exposed sliding sunroof opening.

Otherwise you gotta be out of your mind...... DIY headliner?? It sounds like messing about with stays that hold in place and using specialized tools and technique to tuck and crimp headliner edges after removing fragile fabric door opening weather strips that will probably get destroyed in the process.

Parts = new MB headliner for Heckflosse sunroof car, stays and edge weather strips........ but how much can it cost - maybe $300 + labor?