[Konstantinos]

Indentation is very important, so everyone can read the code properly. I'll explain you what it is!

pawn Код:

public OnPlayerKeyStateChange(playerid, newkeys, oldkeys)
{
new vehicleid = GetPlayerVehicleID(playerid);

    if(newkeys & KEY_SUBMISSION)
    {
    if(GetPlayerState(playerid) == PLAYER_STATE_DRIVER)
    {
    if(nojump2[playerid] ==1)
        {
        return 1;
        }
        }
  }
    return1;
}

It should be readable, like this

pawn Код:

public OnPlayerKeyStateChange(playerid, newkeys, oldkeys)
{
    new vehicleid = GetPlayerVehicleID(playerid);

    if(newkeys & KEY_SUBMISSION)
    {
        if(GetPlayerState(playerid) == PLAYER_STATE_DRIVER)
        {
            if(nojump2[playerid] ==1)
            {
                return 1;
            }
        }
    }
    return 1;
}

So, if you want to open "{", press enter and press tab (4 spaces), write your code and close the brace "}" 4 spaces before, in the line you opened.