[Threshold]

pawn Код:

stock GetName(playerid) 
{
    new name[MAX_PLAYER_NAME];
    GetPlayerName(playerid, name, sizeof(name));
    return name;
}

Then change PlayerName(playerid) and PlayerName(targetid) to GetName(playerid) and GetName(targetid).
You're using two things of the same name, and it's confusing the compiler as to which one you want to use.