The url needs to be called when a lora message is sent to TTN and value1, value2 and value3 would come from the decoded message. If I read: https://www.thethingsnetwork.org/docs/applications/http/ correctly this should be possible but unfortunately the documentation on that page is a bit limited with no real examples to follow.
It would be great if someone could point me in the right direction on how to get the values from the TTN backend to this url format.
I do not think the documentation is telling that you can do it the way you want. HTTP integration sends a JSON message to the endpoint, not data on an URL.
If your really need to send data on the URL, you could write a forwarder to be placed on some server that decodes JSON and sends the needed fields to your endpoint via URL.