2001 Buick Century trunk

Are you saying the trunk won't shut all the way or the trunk won't lock when you do shut it?

If it won't close all the way, then you'll need to look at the mounting hinges and the rods that are connected to each side. One/more of them may be bent or caught up on something.

If it will close but not lock, then check the locking plate. There's a metal ring mounted te the back/floor of the trunk. Sometimes this will get bent. If it is, try bending it back. Then check the locking mechanism that's mounted to the underside of the trunk. This may be bent as well, or the locking catch may be in the wrong position. You could try bending it back or moving the catch until it's in the right position.