Open Settings

Search for the word Power or click System:

Here you will find all settings for sleep mode. Make sure everything is NEVER.

There is another place where you can look:

At the same time press the Windows-key + the key R

Enter: control.exe and click OK

Select System

Select Power Options

The choices you see there may vary per computer, but choose an option such as "high performance"

You can optionally click on Details to see exactly what the option means: