Hi thank you all for your precious support! I'm really glad I'm in this community!

I'm gonna study all the suggestions in detail, please find here attached my part.
I'm also attaching* a screen recording (hope it's more suitable to understand what I mean) for 2 weird things (IMHO)
*uploading on youtube: https://youtu.be/zDpo6_-guAg

- sweep with one rail creates a hashtag like surface? why??
- sweep with 2 rails creates what I'd like to have, BUT, as you can see there isn't ONE object, but TWO? I don't get why... and I don't get how to get those two as one single object... I tried the two first ideas I went up to, with no luck...

I'm sure I'm missing some philosophical view of MOI that would help me immediately grasp what I should expect from every action...
I'd like to immediately, intuitively grasp WHEN sweeping a closed curve won't create a solid, but a joined surface...
Any good online course for that? Maybe a deep dive into understanding nurbs and topology problems?

 

THANKS AND LOVE -- THANKS AND LOVE -- THANKS AND LOVE -- THANKS AND LOVE -- THANKS AND LOVE --