How to get over level 40 (The Witcher 3: Wild Hunt)

I finished the game by completing all the quests that I found from all the boards, exclamation marks, and, well, side effects from the main ones. Earned level 37. There are several items in the recipes for level 45. Is it the developers who have prepared a springboard for upcoming additions, or because of bugs, many quests do not give experience? It's a little stupid - for several hours to complete witcher orders several levels higher for a miserable crumb of experience (5 points, for example) and get a dozen level ups for drinking in Kaer Morhen