Just so you know, we don't know the file format for every file. If it's just a bunch of random characters, it's probably a .zip or .jar.

on skript load:
  set {arena.use} to false
command /duel [<text>] [<player>]:
  trigger:
    if arg-1 is not set:
      send "&cCorrect usage: &e&l/duel (invite/accept/deny) (player)" to player
    if arg-1 is "invite":
      if arg-2 is not online:
        send "%arg-2% is not online"
        stop
      if arg-2 is "%player%":
        send "&c&lYou cant invite yourself to duel!"
        stop
      {duelarena.pos1} is set
      {duelarena.pos2} is set
      {duel.lobby} is set
      if arg-2 is not set:
        send "&cPlease give a player name. Correct usege: &e&l/duel (invite/accept/deny) (player)"
      else:
        set {%player%.inviteduel.%arg-2%} to true
        send "&3Invite send to %arg-2%! &e&lInvite expires in &c30&e seconds!"
        send "%player% wants challenge with you. &e&l/duel (accept/deny) %player%" to arg-2
        wait "30 seconds" parsed as timespan
        {%player%.inviteduel.%arg-2%} is true
        send "&cYour Duel invite to &3%arg-2% &cis expired" to player
        send "&cYour Duel invite from &3%player% &cis expired" to arg-2
        set {%player%.inviteduel.%arg-2%} to false

    if arg-1 is "accept":
      if arg-2 is not set:
        send "&cPlease give a player name. Correct usege: &e&l/duel (invite/accept/deny) (player)"
      else:
        if {%arg-2%.inviteduel.%player%} is true:
          set {%arg-2%.inviteduel.%player%} to false
          if {arena.use} is true:
            send "Sorry, arena is on use. Wait small bit and try again" to player
            send "Sorry, arena is on use. Wait small bit and try again" to arg-2
          else:
            set {arena.use} to true
            send "&3Your Duel invite has accepted by &c&l%player%" to arg-2
            clear player's inventory
            clear arg-2's inventory
            set {induel.%player's uuid%} to true
            set {induel.%player's uuid%.player2} to arg-2
            set {induel.%arg-2's uuid%} to true
            set {induel.%arg-2's uuid%.player2} to player
            add 1 to {gamesp.%arg-2's uuid%}
            add 1 to {gamesp.%player's uuid%}
            teleport player to {duelarena.pos1}
            teleport arg-2 to {duelarena.pos2}
            wait 5 tick
            selectkit(arg-2, player)


        else:
          send "&3%arg-2% &care not send a invite to you or invite expired!"
    if arg-1 is "deny":
      if arg-2 is not set:
        send "&cPlease give a player name. Correct usege: &e&l/duel (invite/accept/deny) (player)"
      else:
        if {%arg-2%.inviteduel.%player%} is true:
          send "&3Your Duel invite has denyed by &c&l%player%" to arg-2
function selectkit(p: player , sp: player):
  open chest with 1 row named "&cSelect kit" to {_p}
  format slot 1 of {_p} with diamond sword named "&cDefault Kit" to close then run [set {%{_p}%.kit} to "Default"]
  format slot 7 of {_p} with bow named "&cOnly Bows" to close then run [set {%{_p}%.kit} to "OnlyBow"]
  if {%{_p}%.kit} is "Default":
    set slot 0 of {_p} to diamond sword named "&c&lDuel Sword!"
    set slot 1 of {_p} to bow named "&c&lDuel Bow"
    set slot 8 of {_p} to 64 arrow named "&c&lDuel Arrow"
    set {_p}'s helmet to diamond helmet of protection 2
    set {_p}'s chestplate to diamond chestplate of protection 2
    set {_p}'s leggings to diamond leggings of protection 2
    set {_p}'s boots to diamond boots of protection 2
    set slot 0 of {_sp} to diamond sword named "&c&lDuel Sword"
    set slot 1 of {_sp} to bow named "&c&lDuel Bow"
    set slot 8 of {_sp} to 64 arrow named "&c&lDuel Arrow"
    set {_sp}'s helmet to diamond helmet of protection 2
    set {_sp}'s chestplate to diamond chestplate of protection 2
    set {_sp}'s leggings to diamond leggings of protection 2
    set {_sp}'s boots to diamond boots of protection 2
    send "&cGame can begin!" to {_p}
    send "&c%{_p}% selected Default kit" to {_sp}
  else if {%{_p}%.kit} is "Default":
    set slot 0 of {_p} to bow of infinity 1
    set slot 8 of {_p} to 64 arrow named "&c&lDuel Arrow"
    set slot 0 of {_sp} to bow of infinity 2
    set slot 8 of {_sp} to 64 arrow named "&c&lDuel Arrow"
    send "&cGame can begin!" to {_p}
    send "&c%{_p}% selected Only Bows" to {_sp}
command /duelsetspawn [<number>]:
  trigger:
    if player has permission "duel.admin":
      if arg-1 is not set:
        send "&cCorrect usege: &3&l/dueladmin (1-2)" to player
      if arg-1 is not set:
        send "&cCorrect usege: &3&l/dueladmin (setspawn) (1-2)" to player
      if arg-1 is 1:
        set {duelarena.pos1} to player's location
        send "&3Spawn &l1 set" to player
      if arg-1 is 2:
        set {duelarena.pos2} to location of player
        send "&3Spawn &l2 set" to player
    else:
      send "&cSorry, but you dont have permission to do that!" to player
command /duelsetlobby:
  trigger:
    if player has permission "duel.admin":
      set {lobby} to location of player
      send "&c&lLobby set to your location! (%player's location%)"
    else:
      send "&cSorry, but you dont have permission to do that!" to player

on death:
  victim is player
  {induel.%victim's uuid%} is true
  set {induel.%victim's uuid%} to false
  set {induel.%attacker's uuid%} to false
  add 1 to {wins.%attacker's uuid%}
  add 1 to {loses.%victim's uuid%}
  send victim title "&cDefeat!" with subtitle "&eBetter luck next time!"
  send victim title "&eVictory!" with subtitle "&eGG!"
  set {arena.use} to false
  clear victim's inventory
  clear attacker's inventory
  teleport attacker to {lobby}
  force respawn player
  wait 1 tick
  teleport victim to {lobby}
  clear victim's inventory
  set victim's health to 20

command /profile:
  trigger:
    if {gamesp.%player's uuid%} is not set:
      set {gamesp.%player's uuid%} to 0
    if {wins.%player's uuid%} is not set:
      set {wins.%player's uuid%} to 0
    if {wins.%player's uuid%} is not set:
      set {wins.%player's uuid%} to 0
    wait 5 ticks
    open chest with 1 row named "&3&lProfile: &b%player%" to player
    wait 3 ticks
    format slot 0 of player with red glass named "&" to close
    format slot 1 of player with red glass named "&7" to close
    format slot 2 of player with red glass named "&7" to close
    format slot 3 of player with arrow named "&7Loses: &c&l%{loses.%player's uuid%}%" to close
    format slot 4 of player with diamond named "&7Wins: &e&l%{wins.%player's uuid%}%" to close
    format slot 5 of player with red glass named "&7" to close
    format slot 6 of player with red glass named "&7" to close
    format slot 7 of player with blaze rod named "&7Games played: &3&l%{gamesp.%player's uuid%}%" to close
command /duellobby:
  trigger:
    {induel.%player's uuid%} is false
    teleport player to {lobby}