"I need to turn off my computer."

Translation: Ninahitaji kuzima kompyuta yangu.

[CliffordPereira]

Why kuzima and not kuwasha, also kuzima is not in the prod.

[AGreatUserName]

Kuwasha would be to turn on. It's the opposite of kuzima. I can't see the prompt you saw though, so if you see it again and it suggests "kuwasha" for "turn off", report it. :-)

[JohanAnder26]

It says kuwasha = to turn. So it doesn't translate "off" which is why one is lead to believe kuwasha could be right

[Rasla143]

kuwasha always means to turn on

[Baziraake]

I would suggest "kuzimisha"