Setting it up takes far longer than 20 minutes.
Our figure of 20 to 25 minutes assumes an electric pump and a little practice. We had not spelled that out everywhere — we are doing so here. If you inflate the hulls by hand, add around 15 minutes. That puts you at roughly 35 minutes. For your very first build, plan 45 to 60 minutes.
The electric pump is an accessory and costs 149.99 euros. It is by far the biggest single time factor when setting up — if build time matters to you, it is the most sensible addition to the boat.
What else speeds it up: keep to the order of the steps, lay out all the parts beforehand — and practice. By the second or third time the routine sits.