btw the setup you can do it by gui or by commands
discord for ideas or bug fixes https://discord.gg/4nUxRdcEPt

commands in game
/duelz Open the main menu GUI
/duelz help Display the help menu
/duelz <player> Challenge a player to a duel
/duelz accept Accept an incoming duel invite
/duelz deny Deny an incoming duel invite
/duelz queue <ranked | unranked> Join the ranked or unranked matchmaking queue
/duelz leave Leave the queue
/duelz spectate <player> Spectate a player's active duel
/duelz stats [player] View your own stats or another player's stats
/duelz profile [player] Open the profile GUI for yourself or another player's profile

and there is more but i couldnt write all of them you can check them inside the game

permissions in game

duelz.admin
duelz.arena
duelz.kit
duelz.use
duelz.spectate

and don't forget the permissions that you will do for the kits since you can't see them at all.