allright, im trying to make a Final fantasy game (not named yet) and im having trouble with the battle system,

for 1; i dont know how to create a new battle feild based on a pre-made one, while it placing it on another Z-level and not overlapping another battle-in-progress.

and second; i dont really understand that much about the on-screen menue and stuff like that, found in other final fantasy games.

can anyone help me, or explain what i need to do, [note: i am not asking for direct coding, just expanation, Although coding would help and save an immense load of work]

thank you.