Is it possible to use a Mac Mini with a laptop monitor?
VNC

You can use VNC on your Mac Mini to show the screen on your Windows or Linux laptop:


  VNC is an abbreviation of Virtual Network Computing. VNC is a common protocol that allows computers to both share and to offer control over the network. Using VNC you can connect to and see your computer remotely; great for remote working or helping a relative perform tricky tasks without needing to be in the same location.
  
  Mac OS X includes a built-in free VNC server. You can set up and use VNC on your Mac without needing additional or third party software.


There are numerous Windows and Linux VNC clients you can use on your Lenovo laptop.

Also see answers to these related questions:


Is it possible to use a Mac Mini with a laptop monitor?
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