I am trying to port forward for using remote desktop but it does not seems to work. I am applying the configuration right but when I check if the port is open it appears to be closed
You need to give more information and possibly a couple of screen shots too.
What firmware are you using? What other features and options are you using on the router? Have you been toggling features on/off (some options may not turn fully off...), without doing a full reset afterward?