The following tutorial will show you the simplest way to install a desktop environment on Debian 9.
The installation
> Please log in Debian server and switch to root
user@debian9:~$ sudo -i
> Please use tasksel tool to install desktop environment
root@debian9:~# tasksel
> You will see a list for choosing the various desktop environments. Simply pick one of the desktop environment such as XFCE and make sure to check 'Debian desktop environment' also. Start to install the software by clicking 'ok'.
> Please reboot the server and then you may log in XFCE.
root@debian9:~# reboot
Desktop Remote Login
> Please install XRDP and TigerVNC server
root@debian9:~# apt-get install xrdp tigervnc-standalone-server
> Please Enable and start XRDP service
root@debian9:~# systemctl start xrdp
root@debian9:~# systemctl enable xrdp
> Start a Remote Desktop Connection session from Windows to connect the server.
