How to attach the edge of those two yellow objects. The right one has to be changed and its edge has to be attached on the edge of the left object. The right one has to be straightly stretched. And there are multiple points in the right one and it is curved.
How to do that?
I cannot find it on the internet, maybe my search words are not right.
How much experience with Rhino do you have? Have you completed any training?
It is difficult to understand your question by only looking at the picture. Can you upload the .3dm file? Use the vertical arrow icon above where you type text for posts.
Offhand I would say MatchSrf the right object to the left one with position option, but the result will depend on the control point structure of the right surface.
When I try to use MatchSrf I cannot select the edges like the people do on the internet. So, probably my lines are not acting as a surface. I thought I can make a surface of lines by using ‘patch’, but still, when I use MatchSrf it does not work like what the internet shows me.
The objects in your file are polylines and curves, not surfaces. Polylines and curves are different types of objects than surfaces. This page describes the different types of objects in Rhino: http://docs.mcneel.com/rhino/mac/usersguide/en-us/index.htm MatchSrf works on surfaces only.
The simplest way to transform the object as you desire would be to redraw it.
The surfaces you created are trimmed surfaces. MatchSrf can only change untrimmed surfaces. My guess is you made the surfaces using PlanarSrf. You can make untrimmed surfaces using your curves with Loft or Sweep2.