tag @s remove player
scoreboard players reset @s player
tellraw @s [{"text":"\n["},{"color":"dark_aqua","text":"System"},{"color":"white","text":"] "},{"color":"white","hoverEvent":{"action":"show_text","value":[{"text":"","color":"dark_red","bold":true,"italic":false}]},"text":"Du bist kein registrierter Teilnehmer mehr."}]
