In all the talk of graphical downgrades no one seems much preoccupied with 'why?'. Why build something and then proceed to tear it down, piece by piece, in the hope that ever more diminished expectations about the final product won't be severe enough to...
Always be quick in dealing with levels! At first take your time to work out how to drop the pieces to complete it. Then when you know what you are doing go back and start the level over and do it as fast as possible.
Use the small reset button on the bottom right of the screen, this resets the clock and lets you start over.
Play the game, practice and you will soon be completing all the levels.