it’s not a simple fix. you have to properly tempo map it. this requires some intermediate to advanced skills using an editor. you can look through these very forums for tips, advice and help with tempo mapping, but really, the bottom line is, you’re gonna have to learn how to author a custom to fix that thing. it’s pretty much the first thing you do when authoring. even after you fix the tempo map, you could end up having to readjust everything anyway, so time to get in the game. =-)
You are about to leave Rhythm Gaming World and access the external songs DB. While no song or file sold for commercially available videogames is hosted there and only fan generated content is allowed, Rhythm Gaming World has no direct control over the database and no files are hosted here. Alright, we had to made you aware of this, now you can visit the database!