[HELP] Bus Driver Job

Hello ! I need you help in this script. First of all, I am not a good scripter, that's why I am asking you why this is not working properly. When two players are playing, one can steal bus stops from other. Also, when one leaves his bus, the other one will not see the markers. Can you help me, and explain everything as I was the dumbest person in the world ?

-----------------------------------------------<< 
-- MTA : Multi Theft Auto : Emanuel's Server 
-- Date: 21 July 2015 
-- Resource: [MTA][Jobs]/[MTA]BusDriver/server.lua 
-- Type: Server Side 
-- Author: Emanuel Camacho 
-----------------------------------------------<< 
local busses = {[431] = true, [437] = true} 
local rootElement = getRootElement() 
  
local markers = { 
[1] = {-1798.63940, 83.94303, 15.10938}, 
[2] = {-1800.16284, 102.19742, 15.10938}, 
[3] = {-1800.60095, 126.91389, 15.10938}, 
} 
  
function getNewBusLocation( thePlayer, ID ) 
    local x, y, z = markers[ID][1], markers[ID][2], markers[ID][3] 
    triggerClientEvent(thePlayer,"setNextBusStopPosition",thePlayer,x,y,z) 
end 
  
function onVehicleEnter(client) 
    if not busses[getElementModel(source)] then return end 
    if not getPlayerTeam(client) then return end 
    if getTeamName(getPlayerTeam(client)) == "Bus Driver" then 
        local x, y, z = getNewBusLocation(client, 1) 
        setElementData(client,"busData",1) 
    end 
end 
addEventHandler("onVehicleEnter",rootElement,onVehicleEnter) 
  
addEvent("updateBusStop",true) 
addEventHandler("updateBusStop",rootElement, 
function (client) 
    if not isPedInVehicle(client) then return end 
    if not busses[getElementModel(getPedOccupiedVehicle(client))] then return end 
    givePlayerMoney(client, 100) 
    if #markers == tonumber(getElementData(client,"busData")) then 
        setElementData(client,"busData",1) 
    else 
        setElementData(client,"busData",tonumber(getElementData(client,"busData"))+1) 
    end 
    getNewBusLocation(client, tonumber(getElementData(client,"busData"))) 
end) 

-----------------------------------------------<< 
-- MTA : Multi Theft Auto : Emanuel's Server 
-- Date: 21 July 2015 
-- Resource: [MTA][Jobs]/[MTA]BusDriver/client.lua 
-- Type: Client Side 
-- Author: Emanuel Camacho 
-----------------------------------------------<< 
local client = getLocalPlayer( ) 
local rootElement = getRootElement() 
local marker = nil 
local blip = nil 
  
function createNextStop ( x, y, z ) 
    marker = createMarker(tostring(x), tostring(y), tostring(z)-1, "cylinder", 3.5, 255, 255, 0, 170) 
    blip = createBlipAttachedTo( marker, 0, 2, 255, 255, 0, 255 ) 
    addEventHandler("onClientMarkerHit",marker,onBusStopHit) 
end 
  
addEvent("setNextBusStopPosition",true) 
addEventHandler("setNextBusStopPosition", rootElement, createNextStop ) 
  
function onBusStopHit( hitPlayer ) 
    if not hitPlayer == localPlayer then return end 
    triggerServerEvent("updateBusStop",localPlayer,localPlayer) 
    if isElement(blip) then destroyElement(blip) end 
    if isElement(marker) then 
        removeEventHandler("onClientMarkerHit",marker,onBusStopHit) 
        destroyElement(marker)  
    end 
end 
  
function leavingVehicle() 
    if isElement(marker) then 
        removeEventHandler("onClientMarkerHit",marker,onBusStopHit) 
        destroyElement(marker)  
    end 
    if isElement(blip) then destroyElement(blip) end 
end 
addEventHandler("onClientVehicleExit",rootElement, leavingVehicle ) 

You must create marker on server-side

marker createMarker ( float x, float y, float z [, string theType = "checkpoint", float size = 4.0, int r = 0, int g = 0, int b = 255, int a = 255, visibleTo = getRootElement( ) ] ) 

visibleTo will be who started bus job