i need some help/ explaination

[Headless]

void OnStart()
{
AddUseItemCallback("Player", "DoorLocked", "DoorOpenSlamming", "DOORopen", true);
AddUseItemCallback("", "DoorLocked", "SlammingSound", "DOORopenSOUND", true);
AddUseItemCallback("", "Key", "Door", "UseKeyOnDoor", true);
}

void UseKeyOnDoor(string &in asItem, string &in asEntity)
{
SetSwingDoorLocked(asEntity, false, true);
RemoveItem(asItem);
}

void DOORopen(string &in asParent, string &in asChild, int alState)
{
SetSwingDoorClosed("DoorOpenSlamming", false, false);
SetSwingDoorDisableAutoClose("DoorOpenSlamming", true);

PlaySoundAtEntity("SlammingSound", "joint_door_move_special.snt", "DoorOpenSlamming", false);

Addtimer("", 2, "TimerStopSound");
AddTimer("DoorOpenSlamming", 0, "TimerMoveDoor");
}

void TimerMoveDoor(string &in asTimer)
{
if(GetLocalVarInt("VarDoor") == 10) return;
AddLocalVarInt("VarDoor", 1);

AddTimer(asTimer, 0.03, "TimerMoveDoor");

AddPropForce(asTimer, -70, 0, 0, "world");
}

void TimerStopSound(string &in asTimer)
{
StopSound("SlammingSound", 0.4);
}
I think im closer but im lost again

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Yes exactly that!

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DoorOpenSlamming>DoorB ..........................................Doorlocked>DoorA
----------------------------------------------------------------------------00000--
0
0
0
---------------------------------------------------------------------------00000--
.................................................................................................Door:Where you enter the room