[Matnix]

pawn Code:

if(listitem == 0) // ..

pawn Code:

if(dialogid == DIALOG_SELL)
{
    if(response) // Button 1
    {
        if(listitem == 0)
        {

            if(MeatRob[playerid] == 1)
            {
                GetPlayerMoney(playerid);
                GivePlayerMoney(playerid, 3000);
                SendClientMessage(playerid, Green, "You sold meet, you got 3000$!");
                MeatRob[playerid]=1;
            }
            else
            {
                SendClientMessage(playerid, Green, "You don't have any meat to sell");
            }
            return 1;
        }
        if(listitem == 1)
        {
            SendClientMessage(playerid, Green, "Should display the third altenative (Commands)");
        }
        return 1;
    }

You're indentation are bad correct them for a better look at your script.