Read Xiaomi Aqara door sensor with MQTT from second HA instance

Hi, I am using two instances of HA, one in the office and the other one at home (both on Synology in Docker-Containers). The Networks of the office and home are linked with a VPN. In the office i use multiple door-and-window-sensors from Xiaomi with an Aqara Hub. Now I want to know the status of the sensors (on/off) from the office in the HA-instance at home, so that i can create automations with that stats (e.g. start the light in the bedroom at home when the door in the office is opened during the night. For that i installed Mosquitto on my Synology at home in a docker-container and added in both configuration.yaml:

#MQTT Broker
mqtt:
  broker: xxx.xxx.xxx.xxx
  port: 1883

But now i don’t know what to do further. How is the next step on the HA instance in the office and at home so that i can see the door sensor from office in the instance at home?
Happy for help!

Have a look at

Should do what you’re after

I just need 8-10 sensors so i don’t wanted to use state stream as a bit overpowered.
In the automation.yaml in the office I use this automation for a door-sensor:

- id: '7245276456274576762452'
  alias: Send Status Door to MQTT
  trigger:
  - platform: state
    entity_id:
      - binary_sensor.door_and_window_sensor_ada2
  action:
  - service: mqtt.publish
    data:
      topic: 'office/sensoren/door'
      payload_template: |
        {% if is_state("binary_sensor.door_and_window_sensor_ada2", "on") %} on
        {% elif is_state("binary_sensor.door_and_window_sensor_ada2", "off") %} off
        {% endif %}
      retain: true
      qos: 1

As I can see in the Developer Tools in the HA-instance at home the Status of the door arrives there correctly (on/off). But the binary_sensor I defined in the HA-instance at home gets no update and always shows “closed”. I defined it like that:

# binary_sensor door
  - platform: mqtt
    state_topic: "/office/sensoren/door"
    name: 'Door'
    force_update: true
    qos: 1
    payload_on: "on"
    payload_off: "off"
    device_class: door

Maybe that there is something wrong with my definition of the binary_Sensor. Can someone tell me my error?

While I wrote the last post I was able to find the error by myself. There was one Backslash to much in the state_topic so that there can’t come any information…
Without that backslash it seems to be fine:

# binary_sensor door
 - platform: mqtt
   state_topic: "office/sensoren/door"
   name: 'Door'
   force_update: true
   qos: 1
   payload_on: "on"
   payload_off: "off"
   device_class: door