Carpenter here..I screw any amount of this boards weekly....this is a shocking attempt and clearly has no idea how to do this...first take all that shit they put up down and quick.second find your joist and which way there running (length of timber above the drywall)make a hole have a look ...when ya find which way there running and how far apart they are your golden...your gonna use 70mm drywall screw with a washer trough your new drywall into the joist repeat this process throughout the ceiling using plenty of screws...if that' way isn't possible and your ceiling needs to be lowered(which ya don't want )remove all old drywall and and start joisting it again keeping it as high as possible then the new drywall will be alot easier to install...on my way to work right now and this pic will get some amount of laughs...let us know if ya had the balls to run these monkeys

It's a finished top..you sanded off the finish my good man..never sand a finished product if it doesn't line up with the bolts and biscuits realine it