>>1763817
Well it depends on what you consider to be the prologue
If you mean your journey to Pharos (ice region castle) then it's not that long
If you mean your journey to Pereus (main castle) then yeah it'll take a while
Anything in between will take a couple of hours if you take it slowly or less if you focus on the main quest instead of exploring the map

I suggest you skip the side quests for now and focus on the main quest since you need to finish some of them to make the world harder