[AndreiWow]

You can add a timer for how long the gate takes to open, example if it takes 1/2 seconds for the gate to open make a timer for 1 / 2 seconds, add a variable like this to remember.

Код:

new gateOpen;

if(gateOpen == 1)
{
    add here the code to happen if the gate is opened fully
    gateOpen = 2;
}
if(gateOpen == 2)
{
  add here what to happen if the gate is opening... in the process to open
  SendClientMessage(playerid, -1, "The gate is opening... please way.");
  SetTimerEx("gateOpenTimer", 2000, false, "i", playerid);//the timer
}
if(gateOpen == 0)
{
  add here to happen if the gate is closed.
  gateOpen = 2;
}


forward gateopentimer(playerid);
public gateopentimer
{
   gateOpen = 0;
   This will happen when the gate fully opened or closed.
}

Not sure if it will work well, you have to modify it a bit to suit your system and work for everyone that tries the .
You will need few more variables for it to work well but I gave you an idea.