Sensor template combining attributes not working

Configuration
1

Hi, i have a public transport sensor with attributes.
I like to have the values of two attributes: departure and departures combined into a new sensor
I created a template sensor: tram17_departure, but get a wrong value: unknownunknown

sensor.tram_17_x With attributes:

name: Tram_17_x
stop_code: '5615'
timing_point_code: null
route_code: '32005616'
line_filter: null
icon: mdi:train
destination: DH Statenkwartier
provider: HTM
transport_type: Tram
line_name: Tram 17 - DH Statenkwartier
stop_name: Aletta Jacobsstraat
departure: '10:52'
delay: '0'
departures:
  - '11:07'
  - '11:21'
  - '11:37'
  - '11:52'
  - '12:04'
update_cycle: 60 seconds
credits: Data provided by v0.ovapi.nl
friendly_name: Tram_17_x


template:
  - sensor:
    - name: "tram17_departure"
      icon: mdi:lightning-bolt
      state: >
        {{ (states('sensor.tram_17_x.departure') + states('sensor.tram_17_x.departures')) }}
`type or paste code here`
3

Okay, i restyled my question a bit.
In the meantime i solved the half of my problem, by using the right code in the template sensor,
using state_attr instead off states.

Last part seems to be more difficult to add another attribute to the first one. I think the problem is to add a array to a stringvariable.
so

{{ state_attr('sensor.tram_17_x', 'departure') + "    " + state_attr('sensor.tram_17_x', 'departures') }}

this give unknown, because departures is a array. When using a attribute that is a string works well…

What i want to achive is to show all departure times in a picture entity card. I read that i had to use a template sensor for this. My first trial was to use a picture glance card that can show more then one entities in the picture. Problem with this card (for me) was that i get icons in the glance card and not the departure values… WTH I still can't use entities, gauge or glance card with attributes!. And
Attributes to glance card

template:
  - sensor:
    - name: "tram17_x_departure"
      icon: mdi:lightning-bolt
      state: >
        {{ state_attr('sensor.tram_17_x', 'departure') }}