COLOGNE — Germany’s third largest cinema operator, Ufa Theater, filed for insolvency Monday, hit by low ticket sales and longterm debt.Ufa runs 234 screens with 55,000 seats, a capacity that had already been cut from 90,000. Hamburg-based Ufa tried to merge with rival Cinemaxx last year, but the deal was cancelled, leaving Cinemaxx with a 10% stake in Ufa. Cash-strapped Ufa said it now hopes to lower its rental costs. However, that could be tricky as 45% of Ufa is owned by Volker Riech, landlord of 15 of the cinema operator’s venues. Ufa managing director Stefan Lehman had previously threatened to stop rent payments to Riech.