Jeg slukker for computeren, før jeg går i seng.

I turn off the computer before I go to bed.

Breakdown of Jeg slukker for computeren, før jeg går i seng.

• jeg: I
• før: before
• computeren: the computer
• slukke for: to turn off

Questions & Answers about Jeg slukker for computeren, før jeg går i seng.

Why does slukke need for here — what does slukke for computeren literally mean?

In Danish, you typically turn off a device with slukke for + [device].
So Jeg slukker for computeren is literally like “I switch off the power/operation for the computer,” i.e. “I turn off the computer.”
You can also see slukke used without for when you turn off something like a light: Jeg slukker lyset (“I turn off the light”), but for many appliances/devices Danish strongly prefers slukke for.

Could I say Jeg slukker computeren without for?

It’s generally not the normal choice. For a computer, slukke for computeren is the idiomatic form.
Slukke computeren may sound incomplete or unnatural to many speakers (though you might hear it in very casual speech). If you want to sound native-like, use slukke for.

Why is there a comma before før?

Because før jeg går i seng is a subordinate clause (it has its own subject jeg and verb går). In Danish, a subordinate clause is typically separated by a comma from the main clause:
Jeg slukker for computeren, før jeg går i seng.

Why does Danish use før and not something like here?