Problem with ASUSWRT device tracking

As my coding skills aren’t that gooe, I’m hoping someone can help me with the following:
The usecase: my garden is a point of entrence to our house, but is rather dark at night. So when we come home and it is dark, I would like to turn on a lamp that is installed in the garden and have it turned off after 5 minutes. I own a Asus RT-AC88U, and I would like to use that for tracking devices. In my configuration.yaml I have this:

device_tracker:
  - platform: asuswrt
    interval_seconds: 10
    track_new_devices: yes

In my atomations.yaml I have this:

  alias: lamp tuinkast aan bij thuiskomst 
- id: '1582974603397'
  alias: Lamp tuinkast aan 
  description: ''
  trigger:
  - entity_id: device_tracker.galaxy_a40
    platform: state
    from: not_home
    to: home 
  condition: []
  action:
  - entity_id: light.lamp_tuinkast
    service: light.turn_on
- id: '005'
  alias: Lamp tuinkast aan 
  description: ''
  trigger:
  - entity_id: device_tracker.galaxy_a70
    platform: state
    from: not_home
    to: home 
  condition: []
  action:
  - entity_id: light.lamp_tuinkast
    service: light.turn_on
- id: '004'
  alias: lamp tuinkast uit na 5 minuten
  trigger:
  - platform: state
    entity_id: device_tracker.galaxy_a70
    to: home
    for: 00:05:00
  - platform: state
    entity_id: device_tracker.galaxy_a40
    to: home
    for: 00:05:00
  action:
    service: homeassistant.turn_off
    entity_id: light.lamp_tuinkast

This works -sortof…
When I turn the wifi of my Phone (Galaxy A70) off and on, the lamp is turned on. Sometimes. Dito for my wife’s a40. When it is turned on, it is turned off after 5 minutes - that part seems to work. But I cannot get it to work as reliable as I would hope it would, and this is getting beyond my present coding skills. I assume there is a far better way to make the magic happen, and I would realy like to learn from the pros…