Greatest Story Never Told

[Mercurian]

Got my next riddle but can't determine if I should be re-arranging the letters according to their order in the riddle or position in the alphabet. I've been trying but either time it's not making any sense for me.

AQPMYF KZLD GPS RQQHOFR
Memenugu knows the steps

2 steps forward, one step back. over and over again, until the end

I'm stuck on this but with a different series of letters. I've tried a few things with switching the letters around, but cant figure out exactly what it wants me to do.