function kupWydajnoscV(p: player):
    if level of {_p} >= 300:
        remove 300 from level of {_p}
        give {_p} 1 enchanted book of Efficiency 5
    else:
        send "nie masz takiego LVL-a" to {_p}

command /sklep [<text>]:
    trigger:
        open virtual chest inventory with 1 row named "&9&lSklep dla zawodowców" to player
        make gui slot 4 of player with stone to close then run function kupWydajnoscV(player)