If my song lyrics are too long, how can I shorten them without losing the whole story of my song?

Presumably you've already thought of getting rid of any repetition and unnecessary information. If your chorus is the same each time, you could consider making them all different, using parts of your story from some of your verses, and then getting rid of those verses. But remember, songs don't have to be short. Rock and metal songs can be quite long, and even folk and hip-hop songs can get up to 10 minutes and beyond! You could also consider telling the same story over two to four songs that are meant to be listened to together (or even expanding it to an entire album).