"Guest" was me with a dead cookie.

OK, so the song is fast....but you'll need to learn it slow. Like playing an instrument....when I learned "St Anne's Reel" on the guitar I had to play it initially at less than 1/4 speed, until I'd got it sorted, and then could speed up.

Vocals are the same...you need to imprint them, even if it means singing them horribly under-tempo until they're in your brain.