According to the description, the ceiling is probably wooden. If he is healthy, it is useless to cut him down and make a new wooden one. Strengthen the floor in the attic with, for example, OSB board, I would personally add some sound insulation, perhaps even thermal insulation. By reed ceiling you probably mean a wooden trope beaten with a plow and thrown. It can only be repaired if it is fallen or loose, just put a new palate or rabbi mesh and restore the plaster. Of course, reducing plasterboard is also possible.