[Dignity]

The following compiles, I've added comments to explain why I do things.

pawn Код:

new reducetimer[MAX_PLAYERS]; // timer variable

public OnPlayerUpdate(playerid)
{
    if(GetPlayerWantedLevel(playerid) >= 1)
    {
        reducetimer[playerid] = SetTimerEx("ReduceWantedLevel", 60000, false, "i", playerid);
        // we store it in a variable so we can kill the timer later
    }
    
    return 1;
}

forward ReduceWantedLevel(playerid);
public ReduceWantedLevel(playerid)
{
    if(GetPlayerWantedLevel(playerid) >= 1)
    {
        SetPlayerWantedLevel(playerid, GetPlayerWantedLevel(playerid) -1);
    }
    
    // if player has no wanted level left, kill the timer
    else if(GetPlayerWantedLevel(playerid) == 0) return KillTimer(reducetimer[playerid]);
    // theres no reason for this timer to keep running if they have no wanted level
    
    return 1;
}

If you have any queries, please do ask. Also, I'm not entirely sure but I think it's very dodgy to use timers under OnPlayerUpdate.