Scratch

Hello, I'm having a lot of trouble creating a new version, or versions of the worlds hardest game. I've uploaded a project called 'practice level i'm making' which i uploaded because after ever level you complete (this occurs with all my multi level games) the movement get's 'laggy and slow sloppy. i've tried numerous different things, and nothing works, and i hope this doesnt mean i have to make new levels as completely different projects! HELP? Thank you!