I think I made a mistake with my Chars how can I delete them and create another Party or at least some of them?

First, click Options icon, choose Reset Adventure which sets the game at the beginning. Then go to the Inn and click the Revert Game icon, this brings in the the party members that are grayed out. Add them to the roster by clicking on them. Right click on each and click Delete PC.

That should do it and your new group will be ready to start a fresh game. Also, if you want to keep the gold from the old group, create a new character and pool gold to him/her and also transfer weapons/armor/items.

Have fun!