Possibility to change in-game scenes (spawning objects / changing background) by killing opponents / dialog options

Hello, unfortunately I didn’t find anything about my problem in the forum:

I’m looking for a way to change my scene in the game when something happens: e.g. if I killed enemy X, a tree / stone should spawn in place Y. Or the sky should change from blue to red.
I’ve been looking for a solution to this since yesterday, but I can’t think of anything proper to do …
Thanks for the ideas

You can try this:

public GameObject Bridge;
public GameObject Background1;
public GameObject Background2;

public void KillEnemy(){

    Bridge.SetActive (true); //Active the bridge
    Background1.SetActive (false); //Deactivate the actul background
    Background2.SetActive (true); //Activate the new background

In case you want to spawn an object, and not activate or deactivate it, you must do this:

public GameObject Bridge; //Object from assets
public GameObject Background1; //Object from the scene
public GameObject Background2; //Object from assets

public void KillEnemy(){

    Instantiate (Bridge);
    Destroy (Background1);
    Instantiate (Background2);