Hello togehter.
I rescued Kyte from this big monster, but what should I do after the scene with rummy and the bird who brings a message to Beak and Fang? I heard something about
Alter-Dimension, but I don't know what it means...
Is anyone able to help me?

After that happens, you'll have to wait until the time cycle ends and you start from the beginning. When your in the Inn, Rinna will knock at your door telling you that there is someone waiting for you in the hotel lobby. When you go down stairs, you'll find yourself with Beak. Later on in the game, when you fight with Twinboom, Fang will automatically join your party. Fang and Beak aren't really necessarily to complete the game, moreover they are secret characters .