Ok so youre missing another one of the floor 2 pieces. Uh oh the level is long and confusing it is soo tough to decribe how to get your missing piece. I hope Petoe would have done some maps of this game. But the boss is easi to find. From the entrance go right and 2 screenies north and then upstairs. Follow the linear route and you should end up to the north part of Floor 1 where you have to blow up a broken shutter. But if you haven't opened the 2 shutters in B1 yet then you cannot reach the boss room yet.