Here’s a very useful word that you can get a lot of mileage from: わからない, or wakaranai.
It seems a bit long in English, but Japanese characters can be broken down into individual sounds for easier pronunciation. For example, わ-か-ら-な-い is five characters, so it’s five sounds: wa-ka-ra-na-i. The “i” is pronounced “ee,” like how you say “cheese,” but in staccato.
So next time your coworker asks you about the TPS report you should have sent last week, just tell them “wakaranai” and let them figure it out.