Hi Olga,

> If you do the same with sphere and cone and join/boolean union
> them together to create one solid - will it work? It does not for me -
> I might be doing something wrong

Do you have the .3dm model file for this that you can post please?

It's pretty difficult to follow along just from the descriptions alone.

This may be something that will confuse the booleans and you may need to switch to a more surface style of modeling - that's where you use Edit/Separate to break solids down into individual surfaces and work on trimming surfaces one at a time to produce what you need.

It's kind of a more "low level" approach than the boolean type operations, but it can let you make progress if you are having problems with the booleans.

Similarly you may be able to make some progress by breaking things into individual surfaces and then using Offset to build some pieces to work off of to do further trimming, etc..., instead of trying to use Shell which will get confused by the sorts of overlapping pieces.

- Michael