Please format your code with the </> button, or with three backticks (see Rule 11). That preserves indentation and avoids problems like replacement of quotes with “smart quotes”.
Try this:
- platform: rest
resource: http://xxx
name: traveltoxxx
value_template: "{{ as_timestamp(value_json.connections[0].to.arrival)|timestamp_custom('%A %-d. %b – %X', true) }}"