Temperature sensor not displaying info

Hey guys,
I am new to HA and started directly with Zigbee2mqtt. I guess my problem is related to Hass.io in general, so i will ask it here.
My issue is probably because i do not understand the concept of HA. And even after watching alot of movies, reading stuff, i just dont get it.

I got my Zigbee2mqtt server running, and paired one of my Xiaomi temperature sensors. The pairing succeeded because in the Zigbee2mqtt log i see the information coming in every few minutes:

zigbee2mqtt:info 5/19/2019, 10:29:54 AM MQTT publish: topic ‘zigbee2mqtt/0x00158d0002e2647d’, payload ‘{“temperature”:21.6,“linkquality”:115,“humidity”:56.27,“battery”:100,“voltage”:3005}’

So on my Hass.io landingpage i have a few entities on top. Like the Hue Temperature and Motion sensors. Also the Xiaomi temperature sensor is there, butit’s not displaying any information. I would like to display the temperature in the circle.
How do i do that?
I also noticed the Entity ID is “Person.firstname_surname”. Where is this ID coming from? Shouldnt it begin with “Sensor…”?

Question 2: I also have a Xiaomi Door sensor installed. Again, in the Zigbee2mqtt log it shows when the door is closed and opened, but this sensor is not visible on the frontend page at all. When i go to “Settings -> Entities” it’s also not visible there. What am i missing here?

Thanks in advance for the support.