Transforming various meshes into one

And only one closed mesh.
Can I do it?
The boolean has some bugs.

You can join meshes? Is that what you are trying to do?

Select meshes and hit CTRL+J

No, in this case the mesh could be an open mesh. I want a closed mesh.

I suggest you google up blender manuals and read them and then if you cannot find the answer there, post here again.