The length of the DBFZ story can be subjective. It includes multiple arcs and character developments, which can make it feel quite lengthy for some players, while others might breeze through it.
Yes, it is. DBFZ Story Mode has many characteristics of a visual novel. It presents the story through a series of visual elements like character illustrations and backgrounds, along with text - based dialogue and narrative, which are typical features of a visual novel.
I don't have the exact number off the top of my head. But you can usually find that information on dedicated gaming wikis or by reaching out to the game's developers or community managers.