[Mean]

You don't understand what does "you have it twice in your script" mean?

here, let me enlighten you:

pawn Код:

public OnPlayerConnect(playerid) {
    return 1;
}

public OnPlayerConnect(playerid) {
    return 1;
}

You have OnPlayerConnect twice. And when it's a redefinition of constant/macro:

pawn Код:

#define OnPlayerEnterRaceCheckpoint(%0,%1) %0something%1something
#define OnPlayerEnterRaceCheckpoint(%0,%1) %0something%1something

Get it?