Hi Matadem, for hollowing you'll probably need to model he interior surface of the hollowed piece similar to how you have modeled the exterior.

You can generate some offset surfaces for some areas as a shortcut, to do that use Edit > Separate on your object, then Construct > Offset to make offset surfaces, those will then need to be trimmed with each other.

I'm not understanding about the yellow highlighted area, can you please explain that part a bit more?

For wrapping you can use the Transform > Deform > flow to apply a pattern to a single surface, but it will be difficult to use on your shape here since it's made up of multiple surfaces instead of just one.

- Michael