Asking how long something will take isn't unreasonable. We're all trying to manage expectations, at work and outside of it. The easy answer is "by end of day"... every day for a week or two. But can we do better?
When I was less skilled as a developer, it was enough to just stay afloat, learning what I needed for the current day or project. As my skill and confidence grows, I've come to appreciate the extra things in life - like a decent set of docs.
Have you ever gotten into a project, underestimated the difficulty, and found things going sideways? You calmly set it aside and walked away, right? Riiiiighttt...