[Jochemd]

pawn Код:

OnPlayerKeyStateChange(playerid, oldkeys, newkeys)
 if(newkeys & KEY_SECONDARY_ATTACK)
{
enter script
}

You're missing a couple of brackets there. A callback is usually opened with a bracket, so why wouldn't this be?

pawn Код:

public OnPlayerKeyStateChange(playerid, oldkeys, newkeys)
{
    if(newkeys & KEY_SECONDARY_ATTACK)
    {
        // enter script
    }
    return 1;
}