Hard to tell without reading. It could be a new challenge for the main character, a reveal of a secret, or the advancement of a subplot. You'll just have to check it out yourself to know for sure.
Well, chapter 22 could reveal new challenges for the characters or introduce some unexpected twists. Maybe there's a key moment that changes the course of the story. But without reading it myself, it's hard to say for sure.
Chapter 31 of 'A Tree Without Roots' is quite eventful. There's a confrontation between two key characters, and some long-hidden secrets are revealed. It keeps you on the edge of your seat.
I'm not sure exactly what occurs in chapter 30. But you might find out by looking at fan reviews or summaries on manga-related websites. Sometimes fellow fans can provide great breakdowns of each chapter.