Check out this thread for how to post code nicely on the forums: Using code tags properly
If that’s copied n pasted as you have it written, the method names are incorrect. They should be (case sensitive), as: Start and OnTriggerEnter
This is incorrect: using unityengine.scenemanagment;
should be : using UnityEngine.SceneManagement;
There are some more errors, type ‘Scene’ is capitalized, etc…
This is an example of how copy - pasting code can be problematic. 