linux – Google Cloud Platform: How to make sure that the virtual machine continues its calculations after disconnecting from the Internet?

I have created VM Instance in Compute Ingeneer with the following settings:

Machine type:
Custom (8 vCPU, 32 GB memory)

SSD persistent disk:
100 GB

Zoned:
australia South eastern1-b

System:
Ubuntu 18.10 (GNU / Linux 4.18.0-1007-gcp x86_64)

And I have to make huge calculations about it, but there is a problem: every time I'm offline, it stops. The CPU activity decreases (screen capture). It's strange because it's a remote server, so I need an opportunity to run it without my machine being connected to the Internet and looking at the logs and terminal output after a new connection.