Simple Reverse Turtle Query

querySize = {
  length = 40,
  width = 40,
  height = 20
}

currentPos = {
  x = 0,
  y = 0,
  z = 0
}

turtle.refuel()

function forward()
  while turtle.detect() do
    turtle.dig()
  end
  turtle.forward()
end

function up()
  while turtle.detectUp() do
    turtle.digUp()
  end
  turtle.up()
end

function down()
  while turtle.detectDown() do
    turtle.digDown()
  end
  turtle.down()
end

function inventarVoll()
  local itemCount = 0
  for c=1, 16 do
    if turtle.getItemDetail(c) then
      itemCount = itemCount + 1
    end
  end
  if itemCount < 16 then
    return false
  end
  return true
end

function checkInFront()
  return turtle.detect()
end

function returnToWork()
  if currentPos.x > 0 then
    turtle.turnRight()

    for c=1, currentPos.x do
      forward()
    end

    turtle.turnLeft()
  end

  if currentPos.z > 0 then
    for c=1, currentPos.z do
      forward()
    end
  end

  if currentPos.y > 0 then
    for c=1, currentPos.y do
      up()
    end
  end
end

function returnHome()
  if currentPos.y > 0 then
    for c=1, currentPos.y do
      down()
    end
  end

  if currentPos.z > 0 then
    turtle.turnLeft()
    turtle.turnLeft()
    for c=1, currentPos.z do
      forward()
    end
    turtle.turnLeft()
    turtle.turnLeft()
  end

  if currentPos.x > 0 then
    turtle.turnLeft()

    for c=1, currentPos.x do
      forward()
    end

    turtle.turnRight()
  end
end

-- 1x Coal = 80
function JustTheRightAmount(doub)
  local fuelLvl = turtle.getFuelLevel()

  local heimweg = currentPos.y + currentPos.z + currentPos.y
  if doub then
    heimweg = heimweg * 2
  end

  if heimweg + 11 > fuelLvl then
    return false
  end

  return true
end

function dumpThatShit()
  turtle.turnLeft()
  turtle.turnLeft()

  local c = 2
  if turtle.getItemDetail() ~= nil and turtle.getItemDetail().name ~= "minecraft:coal" then
    c = 1
  end

  for cc=c, 16 do
    turtle.select(cc)
    turtle.drop()
  end
  turtle.select(1)

  turtle.turnRight()
  turtle.turnRight()
end

function refuelMe()
  turtle.turnLeft()
  turtle.turnLeft()
  up()

  turtle.suck()

  turtle.select(2)
  turtle.drop()
  turtle.select(1)

  if turtle.getItemCount == 0 and JustTheRightAmount(true) == false then
    os.reboot()
  end

  turtle.refuel()

  turtle.turnLeft()
  turtle.turnLeft()
  down()
end

function moveCheck()
  if JustTheRightAmount(false) == false or inventarVoll() then
    returnHome()
    dumpThatShit()
    if JustTheRightAmount(true) == false  then
      refuelMe()
    end
    returnToWork()
  end
end

dumpThatShit()
refuelMe()
for cy=1, querySize.height do
  for cx=1, querySize.width do
    for cz=1, querySize.length do
      moveCheck()
      turtle.dig()
      forward()
      currentPos.z = cz
    end
    turtle.turnLeft()
    turtle.turnLeft()
    for cz=1, querySize.length do
      forward()
    end
    turtle.turnLeft()
    turtle.turnLeft()
    currentPos.z = 0

    moveCheck()
    turtle.turnRight()
    turtle.dig()
    forward()
    turtle.turnLeft()
    currentPos.x = cx
  end
  turtle.turnLeft()
  for cx=1, querySize.width do
    forward()
  end
  turtle.turnRight()
  currentPos.x = 0

  moveCheck()
  turtle.digUp()
  up()
  currentPos.y = cy
end

for cy=1, querySize.height do
  down()
end
dumpThatShit()
refuelMe()