Joining breps with grasshopper

As i am learning grasshopper on my own i kind of get stuck with
many stupid issues like this:
i made the shape on the attach model in grasshopper because i need to make modifications on it.
the thing is that from some reason i can’t join the breps.
any ideas?

SHAPE 1 FOR JOIN.3dm (1.1 MB)
SHAPE TO (20.5 KB)

You need to make an untrimmed surface, there are different ways to do this, here is a simple (and not accurate) one: (36.2 KB)

i don’t understand what is the problem in your definition but you can create better surface with sweep

SHAPE TO (26.5 KB)

yeah its true,
thank you very much!

thank you !