Hehe I`m not feeling strong in naming things ;) (even in my native non-english language)

Thanks Frenchy for that advice.

I know that method. What if its only open surface with few patches. How to check is it watertight and were is the leak. Is in MoI some command to point me that there is a tiny hole or curves are not connected well?

I have lack of knowledge how investigate small errors where I see that my bevel doesn`t work.