Hello Dave and thank you for the links.
I tried Bevelplus but the Surfaces still are separate. Honestly I don't know where I can project curve on a poly surface.
Edit : Now with the Bevelplus and poly output I have one single object. I cleaned up the mesh a little and tried to smooth and the result looks like this




Edit(2): I've also tried to triangulate the outside face which has no divisions but smooth preview and smooth command don't work correct. Any suggestions for this error ?