Great job on keeping up with things here Olegkap. I bet you could use some help. In particular, I think there is a lack of sample code and clear instructions. The library is HUGE and I believe a little inconsistent. (but hey, at least lots of folks are contributing :-)
I will be sure to append more details to this discussion thread as I push through using various aspects of ssh.net. In the future, if I can help with documentation, perhaps that can be my contribution.
I did get the SynchronizeDirectoriess command working. I was about ready to look at the source code when I realized it was just a matter of correctly specifying the parameters. Having no knowledge of SFTP standards hampered my understanding of the requirements.