천천하다 – to be slow ~히 – -ly ending 천천히 – slowly 하다 – do ~십시오 – Imperative mood (Please) So, you can also translate it as "Do it slowly"
This is translated really weirdly because it's in the formal. It should be something more like "please take your time" or "please proceed slowly".
this is also confusing because the same sentence has other excercises saying "천천히 오십시요" is the translation of take your time.
I agree. That was a really unnatural English sentence. I think the best English translation here would just be "Please slow down"