Is it possible to change the difficulty during the game? (The Witcher 3: Wild Hunt)

At first I played on the difficulty of the Story and fights and noticed it became easier and decided to switch to the penultimate one. But the game already went a little at the beginning, I almost explored all the places in the first location and I go through quests in the second one. And on what difficulty do you recommend playing better? interesting, but not very difficult