@SANTOSH-KUMAR Creating a new topic won't magically get more people replying to it. It still appears under Unread like all the others.
Yes. I'm seeing a few mistakes. nano is a ubuntu command, not an installable package. You're missing nodejs-legacy and npm. It's
./nodebb setup although node app -setup should also work. You are in the wrong folder when running the setup. Note you ran mkdir mynodebb followed by git clone mynodebb, this created another mynodebb folder inside mynodebb.
I recommend you follow the official documentation found here and doing each step carefully and making sure you have no errors at each step. The errors tell you the issue. It may seem daunting, but you get used to it.