I have now learned about Variables and did a lighting tutorial on how to set ambient lighting and spot lights.
Still don't have a clue about collision detection, but anyway here's a remake of the Classic SM64 castle grounds which is a Work in Progress.
That's what it looked like after I added the Ambient light. Before:
I used spot lights for lighting it up, which are now being deleted because I don't need them.
I used Blender 3D for modeling an texturing everything you see in the level. IT works great for making stuff like that.