[Jstylezzz]

Not sure if you totally solved it, but if not, check the following code.
Use SetTimerEx to set a timer with the playerid, like

pawn Код:

SetTimerEx("Resetvar",10000,0,"i",playerid); 
forward Resetvar(playerid);
public Resetvar(playerid)
{
showedmessage[playerid] = 0;
}