How to restrict second user on Virtual Machine entry while first one is logged on

I find a method that the second user cannot "kick of" the first user.

Do you only want one user access the remote desktop at one time? If so, you can set the Group Policy to limit the number of the connections.

Open the Group Policy Editor, Locate to:
Computer Configuration\Administrative Templates\Windows Components\Remote Desktop Services\Remote Desktop Session Host\Connections

On the right pane, double-click Limite number of connections, click Enable, set the RD Maximus Connections allowed to 1.

In this way, the group policy restricts the second user to log on the remote desktop if someone is using the remote desktop.